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Boat Forum / Building / March 2007yamaha 15 vs yamaha 9.9
hi all, Im trying to compare a couple of yamaha 4 strokes, both long shaft, both electric start. the 15 and the 9.9 seem to share a common block, but with a different carb and prop? they have exactly the same weight (50kg), same displacement (323cm3), same compression (9.19:1), different gear ration (2.92 for the 9.9, 2.08 for the 15). is the 15 just a 9.9 with a different carb? are they just as reliable as the 9.9? Im guessing they wouldnt have as much usable thrust as the 9.9 with its bigger prop, but probably a higher top speed? thanks for any and all info, Shaun >hi all, >Im trying to compare a couple of yamaha 4 strokes, both long shaft, both [quoted text clipped - 10 lines] > >Shaun If the intended use is a sailboat, you REALLY want a high thrust model. CWM Shaun, Basically Yes.... The only reason to market a 9.9 is for the "less than 10" market (like Canada). Is there any difference in reliability? I very much doubt that it will ever show up and will very user dependent. Which you choose is your bet. What are going to do with it? Do you want to spend the extra money for the 15? The High Thrust versions are for things that take a great deal of effort to get going through the water. It is like holding a car in second gear. If you are going to push a less than 2 ton sloop, you don't even need the high thrust version (the new Honda HT backs much better than the standard). I push a 4800# centerboard sloop with the board halfway down a 6.0k at just over half throttle at about 1/2g/hr with a Honda 9.9. WOT gets me to 6.2 and empties the tank way faster. A friend bought the new TH and you can tell the difference just as he cranks up, but his cruise is at a higher engine speed and his fuel rate is not as good as mine and on flat water I can be at cruise at the same time. What do I know? Well apart from being a lifelong waterman, I'm also a naval architect and a marine engineer (licensed). Your bet from here. Matt Colie > hi all, > Im trying to compare a couple of yamaha 4 strokes, both long shaft, both [quoted text clipped - 10 lines] > > Shaun  Signaturetarget of diversity victim of affirmative action refugee from the war on poverty minimized by political correctness >Shaun, >Basically Yes.... [quoted text clipped - 26 lines] > >Matt Colie I respectfully disagree with this assessment. For a displacement hull, the high thrust version is so much more suitable that I would not consider a standard thrust model, even if it cost $1000 less. I would not put a car engine in a dump truck, either. You'll find out a Major difference when you need to motor against a 4 or 5 knot current. We can motor (Yamaha High Thrust 9.9) at hull speed in calm waters, and carry on a conversation at normal levels in the cockpit. At idle, it's almost completely silent. There's a big comfort benefit. It also stops the boat very quickly. When people ask me how I like my motor, I tell them it's like having my own personal tugboat along. Another factor is that the 9.9 High Thrust is available with a Xtra long 25 inch shaft. For transom mounting on a lift bracket, that's a big advantage. CWM >> hi all, >> Im trying to compare a couple of yamaha 4 strokes, both long shaft, both [quoted text clipped - 10 lines] >> >> Shaun CW, (I used to live next door to a boat by that name.) I fully respect right and desire to disagree, but the facts are that a two ton sloop (that can actually sail) regardless of hull dynamics does not even need the 10Hp to make hull speed in most weather you would actually ever be in and if it is too rough for that, an outboard will be out of the water half the time. My boat came to me with a 7.5 and the only reason that I changed it to the 9.9xles was for the electric start. The 28" transom height was just nice to have in spite of the small additional weight. (I think nobody make that 28" anymore.) Yes, the high thrust version will always produce more thrust, but always at the expense of crankshaft speed at cruise and always at the expense of top speed (again this may not matter as you have achieved hull speed at less than WOT). That additional engine speed must cause additional fuel consumption (just like running in second gear). By the by, since the Ford B block went away (1968?) all the trucks built in this country have had engines that were common with the passenger automobile production. Matt Colie Lifelong Waterman, Licensed Mariner and Pathological sailor >> Shaun, >> Basically Yes.... [quoted text clipped - 36 lines] >>> >>> Shaun Signaturetarget of diversity victim of affirmative action refugee from the war on poverty minimized by political correctness >CW, >(I used to live next door to a boat by that name.) Yes, I know. Your mother was the "dog lady" of Mystic. >I fully respect right and desire to disagree, but the facts are that a >two ton sloop (that can actually sail) regardless of hull dynamics does >not even need the 10Hp to make hull speed in most weather you would >actually ever be in and if it is too rough for that, an outboard will be >out of the water half the time. Sorry, but my actual experience conflicts with that assertion. >My boat came to me with a 7.5 and the only reason that I changed it to >the 9.9xles was for the electric start. The 28" transom height was just >nice to have in spite of the small additional weight. (I think nobody >make that 28" anymore.) Yamaha makes a 25 inch shaft, but it is not available in the standard F series engines. It is only available in the High Thrust motors which are made specifically for propelling sailboats. >Yes, the high thrust version will always produce more thrust, but always >at the expense of crankshaft speed at cruise and always at the expense >of top speed (again this may not matter as you have achieved hull speed >at less than WOT). That additional engine speed must cause additional >fuel consumption (just like running in second gear). What?!? The high thrust version propels the boat at hull speed at LOWER RPM's than the standard motors. Significantly lower. For sailboats, what you need is GRUNT. >By the by, since the Ford B block went away (1968?) all the trucks built >in this country have had engines that were common with the passenger >automobile production. I think you know and understand EXACTLY what I meant, Matt. For that matter, name one dumptruck that uses a passenger car engine. There aren't any. Dumptrucks use high torque, low RPM engines. Other than very light duty landscaping dumptrucks which are glorified pickups, they almost universally use diesels. >Matt Colie >Lifelong Waterman, Licensed Mariner and Pathological sailor [quoted text clipped - 39 lines] >>>> >>>> Shaun CW, Responses are in line (I don't like to do that but we are getting a little long here. >> CW, >> (I used to live next door to a boat by that name.) > > Yes, I know. Your mother was the "dog lady" of Mystic. Right and I still miss her. >> I fully respect right and desire to disagree, but the facts are that a >> two ton sloop (that can actually sail) regardless of hull dynamics does [quoted text clipped - 3 lines] > > Sorry, but my actual experience conflicts with that assertion. My sample is based on experience with a fleet of S2-7.9 hulls 1, 67, 86, 153, 224?, 346, 415 and 505. This has been a serious discussion in the area as the weeds preclude the effective operation of an inboard version. Several of these have been repurposed as cruisers so engine weight is less critical that all around performance. What class/builder is your experience based on? We have have an interesting data point here. > Yamaha makes a 25 inch shaft, but it is not available in the standard F series > engines. It is only available in the High Thrust motors which are made > specifically for propelling sailboats. Actually, I was just at Yamaha's site. The specifications for the HT and STD are very different and unlike Honda they do not give any propeller information. If the page is correct, the 9.9TH is using less displacement and turning the propshaft way slower (2.08 vs 2.92). So, the engine is running faster. >> Yes, the high thrust version will always produce more thrust, but always >> at the expense of crankshaft speed at cruise and always at the expense [quoted text clipped - 5 lines] > than the standard motors. Significantly lower. For sailboats, what you need is > GRUNT. The propeller shaft is turning less fast, but the engine is running faster (trust me - we had a tach on them) and this is just what you want for maximum thrust at zero speed. All the High Thrust engines I have messed with these days are capable of reaching rated engine speed with the boat stationary (tied to a dock in most cases). The standard configuration engines will not get to rated crankshaft speed at zero boat speed. Yamaha apparently does this with gears, Honda does it with a larger D and smaller pitch on the prop with the same gears (this year was different two years ago). My Honda is actually terrible at this, it won't get to within 500RPM of the torque peak and that is still 1k below the the HP peak. I frequently have to go to WOT when maneuvering just to back it off as soon as the boat is actually moving, but I have to be there anyway. It is quieter underway and does burn less fuel than #346 Jus Ducky (but Lee won't tell me how much). This is the same thing that tugboats do - the don't pull fast, they do pull like hell. The big engines don't turn so slowly because they need to to produce the high torque you keep hearing about, they do so because the physics of moving a piston get in the way. That is why the little VW engine that is the same class as your Volvo 2xxx or Yanmar XGM runs up to 4800 or 5200 redline - it is to make horsepower. Their specific torque is about the same as the little marine engines that you know, but they make a good deal more power - only for about 2500 hrs - a Volvo will do twice that. > I think you know and understand EXACTLY what I meant, Matt. I was trying to stick to a single category, but the GM 4500 is a truck can come with a 7yard box and is available with the 8.1 that is the current big block. >> Matt Colie >> Lifelong Waterman, Licensed Mariner and Pathological sailor [quoted text clipped - 13 lines] >>>>> >>>>> Shaun >The propeller shaft is turning less fast, but the engine is running >faster (trust me - we had a tach on them) and this is just what you want >for maximum thrust at zero speed. In real world use, the High Thrust motor runs at LOWER rpm's. It has a HUGE prop in addition to the lower gears. Do tugboats use small props turning fast, or large props turning slow? A small prop turning fast is better for higher speeds and getting a planing hull up on plane. That's not what is needed for a displacement sailboat hull. It's pretty close to the opposite of what is needed. CWM >I push a 4800# centerboard sloop with the board halfway down >a 6.0k at just over half throttle at about 1/2g/hr with a Honda 9.9. WOT >gets me to 6.2 and empties the tank way faster. A friend bought the new >TH and you can tell the difference just as he cranks up, but his cruise >is at a higher engine speed and his fuel rate is not as good as mine and >on flat water I can be at cruise at the same time. Just looking at your friend's Honda HT gearcase, can you tell a difference between it and yours? I'm wondering if the distance between the prop shaft and the cavitation plate is greater on his HT.... or if Honda just sticks a larger diameter prop and lower ratio gears on the same case. Rick On Mon, 12 Mar 07, Matt Colie wrote: >>I push a 4800# centerboard sloop with the board halfway down >>a 6.0k at just over half throttle at about 1/2g/hr with a Honda 9.9. WOT >>gets me to 6.2 and empties the tank way faster. A friend bought the new >>TH and you can tell the difference just as he cranks up, but his cruise >>is at a higher engine speed and his fuel rate is not as good as mine and >>on flat water I can be at cruise at the same time. On Mon, 12 Mar 07, PhantMan wrote: >Just looking at your friend's Honda HT gearcase, can you tell a >difference between it and yours? I'm wondering if the distance between >the prop shaft and the cavitation plate is greater on his HT.... or if >Honda just sticks a larger diameter prop and lower ratio gears on the >same case. ooookie doke. Getting no response, I finally broke down and called the dealer to ask my question. He tells me, not only are the lower units the same, but Honda doesn't even put lower ratio gears it's high thrust model. The only difference is the prop diameter (9.25" vs 10") and the decal on the cowling. Who'd a thunk it. Rick >On Mon, 12 Mar 07, Matt Colie wrote: >>>I push a 4800# centerboard sloop with the board halfway down [quoted text clipped - 18 lines] > >Rick I guess that's why so many folks prefer the Yamaha High Thrust motors for use sailboats! Yamaha models: F9.9 (regular thrust) gear ratio: 2.08 prop size and pitch: 9.25x10.5 T9.9 (High Thrust) gear ratio: 2.92 prop size and pitch: 11.75x11 That's a pretty substantial diofference, wouldn't you say? CWM PhantMan wrote: >>not only are the lower units >>the same, but Honda doesn't even put lower ratio gears it's high >>thrust model. The only difference is the prop diameter (9.25" vs 10") >>and the decal on the cowling. Who'd a thunk it. >Yamaha models: >F9.9 (regular thrust) gear ratio: 2.08 prop size and pitch: 9.25x10.5 >T9.9 (High Thrust) gear ratio: 2.92 prop size and pitch: 11.75x11 >That's a pretty substantial diofference, wouldn't you say? I would say, uh huh. The reason I asked about Honda is because I have the 20hp model and wondered if I have room to swing a 10" prop. Apparently I do. Might come in handy someday although chances are I'll never use it for anything but scootin' my skiffs around. Standard 9.25" prop works fine for that. Back to Yamaha: I was thinking the 8hp model would be better for a smallish sailboat, say a 22'-25', but now I see it's only 6lbs lighter than a 9.9. Not enough to matter imo. I think I mentioned in some other post that I wish somebody would produce a 2 cycle high thrust 25" shaft engine (I like "light" even more than I like "power"). I once had a 6hp 25" Evinrude on a Catalina 22 that was light (60lbs) but not high thrust. It worked ok in most situations but a large dia, low pitch, four wide bladed prop sure would've been nice. Rick >PhantMan wrote: >>>not only are the lower units [quoted text clipped - 25 lines] > >Rick I agree lighter would be great. I know I would be willing to pay a SUBSTANTIAL premium if Yamaha would build the same 9.9 High Thrust 4-stroke out of high tech alternative materials that would save weight. CWM Rick, You Missed a line Look below: > On Mon, 12 Mar 07, Matt Colie wrote: >>> I push a 4800# centerboard sloop with the board halfway down [quoted text clipped - 18 lines] > > Rick Standard BF model 9.25*8 High Thrust Model 10*6.5 The older TH Hondas had a different gear ratio, I guess they have decided it wasn't worth their while. >Rick, >You Missed a line Look below: You mean: >"Yamaha apparently does this with gears, Honda does it with >a larger D and smaller pitch on the prop with the same gears >(this year was different two years ago)" ? Yep, I read it but I guess it just didn't register somehow. Maybe I still had the old specs in my head... including the XXlong shafts. >The older TH Hondas had a different gear ratio, I guess they have >decided it wasn't worth their while. Apparently. Who knows what goes into a marketing decision like that. Rick >Im guessing they wouldnt have as much usable thrust as the 9.9 with >its bigger prop, but probably a higher top speed? Shaun, as you can tell from the replies so far, we need to know your intended use .... a) pushing a displacement hull b) pushing a planing hull c) combination of both "a" & "b" d) none of the above Rick >>Im guessing they wouldnt have as much usable thrust as the 9.9 with >>its bigger prop, but probably a higher top speed? [quoted text clipped - 7 lines] > > Rick Its intended as the main engine on a thunderbird 26. i am planning to buy second hand, and have seen more of the 15's come up for sale than 9.9's which is what i was hoping for. will be used for general harbour docking as well as motoring longer distances when becalmed. Shaun Maybe I'm looking at a different spec sheet or different year model but..... >the 15 and the 9.9 seem to share a common block, but with a >different carb and prop? they have exactly the same weight (50kg), I'm seeing a heavier 15hp than 9.9hp (granted, I'm looking at specs on short shafts). >same >displacement (323cm3), I'm seeing 362cc for the 15hp, and 323cc for the 9.9hp >same compression (9.19:1), 9.3:1 for 15hp, and 9.19:1 for 9.9hp >different gear ration >(2.92 for the 9.9, 2.08 for the 15). Yep but different RPM ranges. 5000-6000 for 15hp and 4500-5500 for the 9.9hp. >is the 15 just a 9.9 with a different carb? My guess...... no. >are they just as reliable as the >9.9? My guess.... yes. >Im guessing they wouldnt have as much usable thrust as the 9.9 with >its bigger prop, but probably a higher top speed? Depends.... (see my multiple choice post). >thanks for any and all info, Good questions. Glad you asked. BTW, here are the spec sheets I'm looking at: http://www.yamaha-motor.com/outboard/products/subcatspecs/4/specs.aspx http://www.yamaha-motor.com/outboard/products/subcatspecs/5/specs.aspx Rick interesting how you got a different spec page from what i did... i got mine from here http://www.yamaha-motor.com.au/marine/index.htm?marine.asp click on protable 4 strokes, and the two models im comparing are the FT9.9DEL and theF15AEHL. they have the specs i gave before, wondering why the page you've given me shows different specs? Shaun > Maybe I'm looking at a different spec sheet or different year model > but..... [quoted text clipped - 6 lines] > >>same >>displacement (323cm3), > [quoted text clipped - 35 lines] > > Rick >interesting how you got a different spec page from what i did... i got mine >from here [quoted text clipped - 6 lines] > >Shaun You are comparing an "F" series 9.9 to the "F" series 15. The sailboat motor (high thrust) is a "T" series motor. CWM "Shaun Van Poecke" wrote: >>interesting how you got a different spec page from what i did... i got mine >>from here >>http://www.yamaha-motor.com.au/marine/index.htm?marine.asp >You are comparing an "F" series 9.9 to the "F" series 15. The sailboat >motor (high thrust) is a "T" series motor. Actually, the spec sheets are calling both the "F" and the "T" 9.9s "High Thrust" motors. One site is American, the other is Australian. Shaun.... you wouldn't happen to be Australian would you? Either way, methinks you'll need to speak with a product expert with the company. This is gettin' a little too confusing for moi. Rick <----- Gulf Coast MS, USA Charlie Morgan wrote: >>The sailboat motor (high thrust) is a "T" series motor. PhantMan wrote: >This is gettin' a little too confusing for moi. One last thing..... Charlie's right in that the "T"series 9.9 has a 25" shaft. The "FT9.9DEL" comes with a 22.3" shaft. For a sailboat, longer is better. Rick Given the walterline length and displacment of the boat you can calculate the horsepower required to go at any speed. The waterline length and displacement can be found by taking measurements off the hull, or they might be avaiable for the Thunderbird somewhere. I've only done it for sail power, not outboard motor power. I don't know the difference between rated engine horsepower and thrust or whatever number measures the actual power applied to the hull. The point is you can calculate to find the best outboard for a boat. That's the speed in still water in a dead clam. Wind, tides, waves, and current will effect the actual speed. You might need more speed to overcome local tides but a more powerful engine won't make much difference because it's the waterline length and displacement which are the biggest influences on boat speed. Of two engines using the same engine block, the one which produces the required horsepower at the lowest rpm's will last longer and burn less fuel. On second hand engines the other main factor is the cylinder compression which tells how worn the engine is. Measureing the compression is cheap and easy to do, but find out if it has a bypass to make pulling the starter rope easier. Lawn mower engines have this which makes it impossible to measure the cyliner compression. There is a well-known exponential relationship between power and speed on a dispalcement hull. The point of maximum curvature where the power requirement takes off is the "hull speed", equal in knots to 1.34 times the square root fo the walterline length. Commercial operators run their boats at about 60% of hull speed for best fuel economy. >Given the walterline length and displacment of the boat you can >calculate the horsepower required to go at any speed. The waterline [quoted text clipped - 4 lines] >number measures the actual power applied to the hull. The point is you >can calculate to find the best outboard for a boat. Not really. You are leaving out a whole lot of variables in your theory. >That's the speed in still water in a dead clam. Wind, tides, waves, >and current will effect the actual speed. You might need more speed to >overcome local tides but a more powerful engine won't make much >difference because it's the waterline length and displacement which >are the biggest influences on boat speed. Incorrect. A more powerful engine will allow you to keep moving in adverse conditions where a minimal engine will not. That's why you'll find that tugboats (displacement hulls) are pretty much ALL engine below decks. It doesn't make them go faster. The high thrust outboards under discussion produce a lot of thrust by use of a very large, slow turning propeller. Standard outboards use a comparatively tiny prop at High RPM. CWM > >Given the walterline length and displacment of the boat you can > >calculate the horsepower required to go at any speed. <...> > Not really. You are leaving out a whole lot of variables in your > theory. The other variables important when designing the hull, but not when computing the power requirement. Assume it's a well-designed monohull, then all you need is the displacment to calculate the amount of sail to put on the boat, and therefore I claim the size of outboard engine. At 17-21 kt windspeed each sq ft of sail produces 0.04 hp (beam reaching). I'd multiply the area of the sails on the Thunderbird by 0.04 to get the hp requirement. As I mentioned I don't know how to convert that effective hp to the nominal hp of the outboard manufactuer's rating. I was wrong to suggest the waterline length is needed to compute the pwer requirement. Only the displacement is needed. There square root of the sail area divided by the cube root of the dispalcement should be just above 1.0. For dingy's it's 1.3. The ratio is called the Bruce number. Rather surprizingly, wind tunnel tests show there is not much difference in the type of sail on a boat when beam reaching. It's in upwind saiing that some outperform. So the above formula works quite well for all sail plans. And that's why I suggested using the hp rating for beam reaching when sizing the outboard motor. > >That's the speed in still water in a dead clam. Wind, tides, waves, > >and current will effect the actual speed. You might need more speed to [quoted text clipped - 9 lines] > turning propeller. Standard outboards use a comparatively tiny prop at > High RPM. I doubt tugboats have huge engines to overcome adverse conditions, rather to be able to pull and push heavy loads. For "load" read "displacement". Take away the load and the tug's top speed is determined by wetted surface and waterline length, just like every other displacement hull. Because the power requirement quickly rises to infinity additional engine power is useless. At a speed to length ratio of about 1.5 (can't remember exactly) any hull is plaining. Ever see a tugboat plane? :) Because I don't know how to convert nominal to effective horsepower for boat engines I bow to your superior knowledge of rpm's, propellor size, pitch, etc. >For "load" read "displacement" Herein lies the problem. There's more to "load" than "displacement" and some of it is unpredictable. For instance, how much wind will you ever motor against? -shrug- Who knows? And how much current will you ever motor against? -shrug again- Both those factors need to be added to "load" but all you can do is guess at what might be the worst case scenario and plan for that. I think that may be part of the point CWM is trying to make. Another part is, no matter how much horsepower you generate with an engine, if you don't transfer it effectively to the water with a proper prop, the hp is of no use. If I'm reading you correctly though, your theory is for calculating only hp and leaves other "pushing parts" to be calculated by some other theory. yes/no? Whatever the case, my theory is.... you can never have to much power. You can have to much weight though, which is why I wish someone would market a 2 cycle high thrust outboard. Rick On Mar 14, 6:30 pm, Phant...@nospam.invalid wrote: > >For "load" read "displacement" > > Herein lies the problem. There's more to "load" than "displacement" > and some of it is unpredictable. For instance, how much wind will you > ever motor against? -shrug- Who knows? Very true but wind is what makes sails work. (The questioner wanted an outboard for when there was no wind.) Auxilliary power on sailboats is almost exclusively for windless conditions and restricted waters (approaching and leaving moorings, narrow channels, canals, lift bridges, etc.). Wind and waves aren't a good reason for sizing the auxilliary. And how much current will you > ever motor against? -shrug again- Yes, but useful power is limited by the boat's speed to length ratio, where speed is relative to current. Trying to make headway against a current which is about equal to "hull speed" is futile. Thankfully few currents are quite so fast. There is only so much power you can reasonably apply to a displacement hull. Any more and you're just heating the atmosphere and wasting fuel. Another part is, no matter how much horsepower you > generate with an engine, if you don't transfer it effectively to the > water with a proper prop, the hp is of no use. If I'm reading you > correctly though, your theory is for calculating only hp and leaves > other "pushing parts" to be calculated by some other theory. yes/no? Yes, I've noted there has to be a conversion from nominal or rated horsepower to effective horsepower. > Whatever the case, my theory is.... you can never have to much power. > You can have to much weight though, which is why I wish someone would > market a 2 cycle high thrust outboard. Too much weight and fuel consumption, sort of an SUV of a sailboat. Interesting to note that heavier engines increase displacement and add somewhat to power requirement. >On Mar 14, 6:30 pm, Phant...@nospam.invalid wrote: >> >For "load" read "displacement" [quoted text clipped - 9 lines] >bridges, etc.). Wind and waves aren't a good reason for sizing the >auxilliary. Hoo-boy! CWM > On Mar 14, 6:30 pm, Phant...@nospam.invalid wrote: > > >For "load" read "displacement" [quoted text clipped - 9 lines] > bridges, etc.). Wind and waves aren't a good reason for sizing the > auxilliary. I think you should add conditions where tacking is impractical. I have had to do my share of motor sailing into headwinds, and there, the sails were used more for stability than forward thrust. Also, I agree entirely with Charlie Morgan about the effectivitiy of high thrust engines for sailboats. When shopping for a new engine for my 2 ton sailboat, I originally bought a Honda. When I discovered it had a high gear ratio, I returned it and bought the High Thrust T9.9 Yamaha. It is a heavy engine, but I installed an assisted motor mount, which helps a lot. However, I can't lift the engine into the cockpit like I used to do with my Silver Century Seagull, another great sailboat engine with an even higher gear ratio than the Yamaha. I think Honda putting a larger prop on it's 'high-thrust', high gear ratio engine is a poor compromise. It will still churn up a lot of water, with reduced thrust. I prefer having an engine with extra reserve power. I have had too many occurences where my boat could not make headway into very strong winds and/or currents. The only thing I don't like about my T9.9 are the tiny jets in the carburetor, which are continually blocking up. I am actively working on solutions for that, such as fine 10 micron inline filters and changing out my fuel system with newer hoses. Could also be the gasohol we get now, despite doctering it up with stabilizers. Yamaha has not come out with a good fix yet, so I hope my measures will get rid of the problem. Sherwin D. > And how much current will you > > ever motor against? -shrug again- [quoted text clipped - 3 lines] > current which is about equal to "hull speed" is futile. Thankfully few > currents are quite so fast. Guess you have never had to negotiate one of the many 'tidal cuts' in Florida and the Bahamas, or ever tried to go upstream against a strong current on the Mississippi River ( I have). > There is only so much power you can > reasonably apply to a displacement hull. Any more and you're just > heating the atmosphere and wasting fuel. Not if your boat is going slower than it's hull speed. > Another part is, no matter how much horsepower you > > generate with an engine, if you don't transfer it effectively to the [quoted text clipped - 12 lines] > Interesting to note that heavier engines increase displacement and add > somewhat to power requirement. >I can't lift the engine into the >cockpit like I used to do with my Silver Century Seagull Tell me about it. Or it's nice to set it in cabin to lock it up. Plus the tendency to list, and/or squat the stern, and lift the bow, instead of adding stability low and amidships where weight needs to be (I've almost convinced myself to go inboard next time.... but not quite). >I think Honda putting a >larger prop on it's 'high-thrust', high gear ratio engine is a poor >compromise. For you and me maybe. But for them, it's a profit maximizing decision that prolly works pretty well on their bottom line. But at least they're honest about what it'll do. They're claiming only a 15% increase in thrust. Sounds about right to me. >The only thing I don't like about >my T9.9 are the tiny jets in the carburetor, which are continually blocking >up. Honda has the same problem. I spent 30 minutes yesterday cranking and cussin' at mine. Never did get it started. So it's off to the shop with it (again). I no longer have the patience. Hopefully I'll get it back in a few weeks (as opposed to months like last time). Meanwhile I'll putter along with my ol' ancient standby Evinrude. It ALways starts, no prob. >I am >actively working on solutions for that If you come up with one, please post it here. Rick Actually, repairing a blocked carb on the Yamaha is tiresome, but not that difficult. After dissassembly, just run a very fine wire through the jets to open them up. A more pro-active way would be to buy only premium gasoline. Make sure your fuel system is clean, hoses, tanks, etc. Use a stabelizer like Sea Foam or Stabil in the gas tank. Put a fine filter (about 10 micron) in line with your fuel delivery system. I am going to try all the above next season. Now that I hear that Honda's have the same problem, I regret even less my decision to go with Yamaha. Honda is obviously catering to the power boat community. Sherwin D. > >I can't lift the engine into the > >cockpit like I used to do with my Silver Century Seagull [quoted text clipped - 31 lines] > > Rick >Actually, repairing a blocked carb on the Yamaha is tiresome, but not that >difficult. >After dissassembly, ....... (the tiresome part.... as well as reassembly) >just run a very fine wire through the jets to open them up. That's the "not that difficult" part. >A more pro-active way would be to buy only premium gasoline. Make sure your >fuel system is clean, hoses, tanks, etc. Use a stabelizer like Sea Foam or >Stabil in the gas tank. Put a fine filter (about 10 micron) in line with your fuel >delivery system. Honda has a screw on the side of the carburetor that, with a half turn, allows the bowl to drain (thru a tube, out, next to the pee hole... pretty handy :-). My shop sevice manager says that's the most important thing I can do to prevent gum up. "Running" the carb dry won't empty it completely. He mentioned everything else on your list as well. I asked if I could have it back in a few days. He shook his head and said "Maybe a few weeks". Frankly, my money's on "Months", we'll see. Those guys *really* could use some competition around here. If I have some spare time next weekend, I may pick it up and fix it myself (but not at the expense of my warranty... need to check on that). >Now that I hear that Honda's have the >same problem, I regret even less my decision to go with Yamaha. Next time, you might consider Mercury as well. They're building their own powerheads this year (they no longer use Yamaha). And they have two "sailboat" friendly 9.9's (large dia props, low gear ratio, 25" shafts) which seem to be a few pounds lighter than Yamaha or Honda or anybody else I can see. I'm not sure what the difference is between those two models (Bigfoot & Prokicker) except Prokick offers power trim. So Bigfoot is lighter (96lbs). Rick > >Actually, repairing a blocked carb on the Yamaha is tiresome, but not that > >difficult. [quoted text clipped - 14 lines] > turn, allows the bowl to drain (thru a tube, out, next to the pee > hole... pretty handy :-). Yamaha has the same screw. If you are going to be away from the boat for more than few weeks, you should drain the carbs. I don't think that will eliminate the problem, but will minimize it. > My shop sevice manager says that's the most > important thing I can do to prevent gum up. "Running" the carb dry [quoted text clipped - 10 lines] > > Next time, you might consider Mercury as well. I hope there will not be a next time for me as I am getting close to the age of 'shipping oars'. Of course, if I find no solution to this carb problem, maybe the next step is a class action suit against Yamaha. I paid big bucks for this engine and got an unreliable pain in the neck. > They're building their > own powerheads this year (they no longer use Yamaha). And they have > two "sailboat" friendly 9.9's (large dia props, low gear ratio, 25" > shafts) which seem to be a few pounds lighter than Yamaha or Honda or > anybody else I can see. Well, a 'few' pounds won't make a big difference. It remains to be seen just how high (not low) a gear ratio they come up with. My Seagull had a whopping 4 to 1 ratio. No manufacturer has yet come close to that. It seems like all these four strokes have very tiny jets for fuel economy or possibly pollution control. That makes them sitting ducks for blockage. When the outboard gurus come up with a solution for that one, I'm interested. > I'm not sure what the difference is between > those two models (Bigfoot & Prokicker) except Prokick offers power > trim. So Bigfoot is lighter (96lbs). My Yamaha is about 100 pounds, so 96 pounds is no big deal. Sherwin > Rick >> >Now that I hear that Honda's have the >> >same problem, I regret even less my decision to go with Yamaha. [quoted text clipped - 5 lines] > the next step is a class action suit against Yamaha. I paid big bucks for this > engine and got an unreliable pain in the neck. If the problem was with the engines, everybody who owned one would have the same problem. Clearly that is not the case. The first thing I would do in your case is to dump the gas in your tank, clean the tank and check it for rust. Then put in fresh gas using a funnel with a screen. If you are filling your boat from Jerry cans, they may also be the source of the problem. I have two of these motors. One is a 1992, which has had the carb cleaned TWICE in 15 years, and the other is a 2005 that has never had any problems whatsoever in two seasons of use. My opinion, based on that experience is that these engines are EXTREMELY reliable. CWM >a 1992, which has had the carb cleaned TWICE >in 15 years Do you have any tricks that haven't already been mentioned to keep your jets from clogging during non-use? Rick >>a 1992, which has had the carb cleaned TWICE >>in 15 years [quoted text clipped - 3 lines] > >Rick I don't know. I use a filtered funnel (yes, I've observed particles being caught in the filter!) when I fill the tank, and the inside of the tank is clean and rust free. I inspect it each spring with a dental mirror and a flashlight. I ALWAYS add Stabil to gas when I fill up my jerry cans. I also buy my gas from a "land" gas station that does a lot of business, so maybe their gas is fresher? I avoid getting gas from gas docks whenever possible. I'm somewhat suspicious of the fact that gas docks around here sit idle all winter. That may lead to a lot of crap accumulating in their storage tanks that then gets pumped into Sherwindu's boat. ;^) CWM >I ALWAYS add Stabil to gas when I fill >up my jerry cans. I've been hearing about Stabil more and more. I've never needed or used it until now. I've always just run my carbs dry when I get in. If small jets are in my future though, guess I'd better stock up. Does "Stabil" have any competition... any sort of generic stuff, lower price, that can do the same thing? Rick >>I ALWAYS add Stabil to gas when I fill >>up my jerry cans. [quoted text clipped - 6 lines] > >Rick I imagine there are other similar products, but Stabil is very well known, and it works, so I haven't been tempted to try any others. A little goes a long way, so I never considered the cost. I put it in ALL of my small engines, including 2-stroke weed wackers, 4-stroke lawn mowers, etc. As far as the frequently repeated suggestion that 4-strokes have more problems due to "smaller jets"... I would suspect that the jets on a 4.5 HP lawnmower would be a LOT smaller than the jets in a 9.9 HP Yamaha outboard. I find the "smaller jets" theory to be nonsensical, and without any basis in fact. Some people just aren't very careful about keeping particulates and gum out of their fuel tanks. It really doesn't take much effort. CWM >I would suspect that the jets on a >4.5 HP lawnmower would be a LOT smaller than the jets in a 9.9 HP >Yamaha outboard. Speaking of which, my lawnmower carb is first on the priority list tomorrow morning. It cranks easy enough but it's running like crap (already changed the plug and air filter). Rick My lawnmower mechanic warns me not to depend on Stabil for anything longer than a month, or so. It too will loose it's protective abilities. I don't have any problems with my 4 stroke lawnmowers. It could be a factor that the outboards are out there in the sun where the gas gets heated up encouraging particulates to form. I don't think anyone has done a careful study of this, and the outboard people certainly don't want to reveal any defects in their design. Sherwin D. > >>I ALWAYS add Stabil to gas when I fill > >>up my jerry cans. [quoted text clipped - 22 lines] > > CWM Rick, Stabil is good for stored or little used fuel, but it is no substitute for draining or at least running a carburetor dry. Stabil was real good at keeping the tetraethyl lead in gasoline from oxidizing and forming the nasty varnish that used to be such a headache. If you really need to store a carbureted engine when you can not drain the float bowl, get the engine warm and pop the fuel line into some very light oil (Marvel is good) and let it suck that in. When the engine chokes to a smoking halt, all the internals of the carburetor are filled with oil and will not be damaged by moisture or varnished at all. Worked for us for years. I just restarted a SB chevy based marine engine that we had not run for seven seasons and the only tough part was finding my rod to run the oil pump so we could prime the lube system. Matt Colie Lifelong Waterman, Licensed Mariner and Pathological Sailor >> I ALWAYS add Stabil to gas when I fill >> up my jerry cans. [quoted text clipped - 6 lines] > > Rick >Stabil is good for stored or little used fuel, but it is no substitute >for draining or at least running a carburetor dry. That's what I'm thinkin'. I'll just be more diligent than I've needed to be past. I think I must have left gas in the bowl last time because I thought I'd be using the boat again in the next few days. That turned into a couple of weeks and there I am. Rick I almost never buy gas at a boat gas dock. This carburetor problem is somewhat recognized. It may be tied to gasahol. When gasahol was introduced to the NE USA, the incidence of blocked carbs on 4 strokes went up dramatically. I have talked to good mechanics here on Lake Michigan, and they show me 4 stroke engines lined up waiting to have their carbs cleaned. The problem is in these fine jets they use. If you haven't had any problems, you are possibly the exception. Sherwin D. > >>a 1992, which has had the carb cleaned TWICE > >>in 15 years [quoted text clipped - 17 lines] > > CWM > I almost never buy gas at a boat gas dock. This carburetor problem is > somewhat recognized. It may be tied to gasahol. When gasahol was [quoted text clipped - 4 lines] > jets they use. If you haven't had any problems, you are possibly the > exception. To be quite onest: I live in the Netherlands (Europe) and I have never ever experienced anything like a blocked carburettor in the outboards I have owned. At present I have a 6 hp Mercury four stroke outboard. When I have delivered the boat at the yard where it is laid up for the winter, I take the engine home, without having let the carbs run dry, and put it in storage. In spring I put it on the boat, connect it tot the fuel tank (often containing 5 months old gasoline). The engine starts (with good priming) at one or two pulls on the cord and runs perfect ever after. Your problem must be something with the fuel you use. SignatureLodewijk >Your problem must be something with the fuel you use. Seems so. In fact that's my mechanic's theory. His exact words were "the gas we've been getting lately ain't worth crap". I'm not sure who he meant by "we" but maybe he meant our part of the country. That'd make sense if other parts of the world don't have the same problems. I buy most of my gasoline at the Exxon station around the corner. They do a high volume of sales and I doubt gas stays in their tanks very long at all. But it does seem odd that some people have problems with gummy carbs and other people don't. Rick >>Your problem must be something with the fuel you use. > [quoted text clipped - 9 lines] > > Rick Try mixing 5% low sulfur diesel into the fuel. More power and less deposits on the carb. Don't exceed 5% though, or you'll foul plugs. It won't go bad as fast either. Signature“TAANSTAFL” ____________________________________________________________________________ "A prudent man foresees the difficulties ahead and prepares for them; The simpleton goes blindly on and suffers the consequences." - Proverbs 22:3 ____________________________________________________________________________ >It remains to be seen just how >high (not low) a gear ratio they come up with. You say to-may-to, I say to-mah-to. I'd say 4:1 is lower than 2.92:1. >My Seagull had a whopping 4 to 1ratio. Yup, they don't make 'em like they used to. But wasn't it a much lower horsepower engine? It would need all that leverage to push the same load. >No manufacturer has yet come close to that. Not that I know of either. At least not at 9.9hp or above. Your T9.9 is 2.92:1. That's as low as I've seen currently. Mercury is 2:42:1 and Honda is 2.33:1. >My Yamaha is about 100 pounds, so 96 pounds is no big deal. Yamaha spec sheet shows 108. For me, 12lbs might be big enough to tip the balance, all else being equal. Rick > >It remains to be seen just how > >high (not low) a gear ratio they come up with. [quoted text clipped - 6 lines] > horsepower engine? It would need all that leverage to push the same > load. I remember advertising pictures of these larger Seagulls pushing heavily laden barges. True, it would take them time to get the vessels moving, but they had the torque to do the job. The only problems with the Seagulls were the mixing of the gas and oil, and the annoying noise and vibration. They were simple to fix. I even rebuilt the lower gear box on one going down the Mississippi, and I'm not an experienced mechanic. > >No manufacturer has yet come close to that. > [quoted text clipped - 6 lines] > Yamaha spec sheet shows 108. For me, 12lbs might be big enough to tip > the balance, all else being equal. Actually, I looked up the weight in my 2002 Yamaha catalog and the T9.9 high thrust engine is listed as 99 pounds. > Rick |
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