 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeDiscussion GroupsBoatsPaddle BoatsSailingCruisingBuildingElectronics Related Topics CarsMotorcyclesMore Topics ... |
Boat Forum / Cruising / July 2004Yamaha 9.9 outboard runs smooth then sputters
Hi everyone, With the wealth of knowledge and experience here, I have a problem that needs your insight. My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs fine at lower RPM, but when I ramp up over 35% of max speed the engine will invariably run fine for 20-40 seconds and then cough, sputter, slow for a few seconds and then speed back up. The faster the RPM, the more frequent the problem. Sometimes pumping the sqeeze bulb on the fuel line will solve the problem for a short while, but not always. I immediately suspected a fuel line problem, but the filters are all clean (in engine and in gas tank), the hose seems to be clear, and just to make sure I also changed the spark plugs and oil. The only think I can think of is that it could be sucking air somehow. Any suggestions would be extremely welcome! Thanks, and fair winds, Mike > My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs > fine at lower RPM, but when I ramp up over 35% of max speed the engine [quoted text clipped - 4 lines] > Sometimes pumping the sqeeze bulb on the fuel line will solve the > problem for a short while, but not always. Sounds like a blocked tank breather to me. On small outboards the breather is often a small hole in the fuel filler cap. If this is blocked or if you have the wrong fuel cap there will be a vacuum in the tank as fuel is pumped out into the engine. The simple test for this is to loosen the filler cap. Some tanks have a finger screw on the cap which you need to open when running the engine.  SignatureMy real address is crn (at) netunix (dot) com WARNING all messages containing attachments or html will be silently deleted. Send only plain text. Sounds like a weak fuel pump or a sticking needle and seat in the carb. Dennis >Hi everyone, >With the wealth of knowledge and experience here, I have a problem that [quoted text clipped - 19 lines] >Thanks, and fair winds, >Mike Another possibility is bad gas, being either old or contaminated. Try a fresh tank. Sherwin Dubren > Hi everyone, > With the wealth of knowledge and experience here, I have a problem that [quoted text clipped - 19 lines] > Thanks, and fair winds, > Mike Thanks everyone! The gas was new last weekend, so I don't think that's the problem. I'll check the other things when I get back into town tomorrow. Thanks again, Mike > Hi everyone, > With the wealth of knowledge and experience here, I have a problem that [quoted text clipped - 19 lines] > Thanks, and fair winds, > Mike > Thanks everyone! The gas was new last weekend, so I don't think that's > the problem. I'll check the other things when I get back into town > tomorrow. > Thanks again, Mike, When you speed up the motor, does applying a little choke let it go to higher RPM's? I had this problem a couple times as the motor sits on the pushpit most of the time and what is left in the carburator gums it up. I always turn the gas off and run it till it quits, but after a few months the problem is back again. Leanne Leanna, I thought of using the choke too, and tried it last night. It didn't do any good. But it could be that the carb is gummed up. I'll add that to my list of things to check. Thanks! >>Thanks everyone! The gas was new last weekend, so I don't think that's >>the problem. I'll check the other things when I get back into town [quoted text clipped - 9 lines] > > Leanne >Thanks everyone! The gas was new last weekend, so I don't think that's >the problem. I'll check the other things when I get back into town >tomorrow. >Thanks again, >Mike Another possibility which happened to my four-stroke Honda 9.9 is a stuck carb float, which make for harder starts, limited acceleration and the occasional stall. It needed a good clean due to crap in the gas. Filtering the gas/cleaning the tank is always a good idea. R. Factory prop or did you change it for one with a different pitch? > >Thanks everyone! The gas was new last weekend, so I don't think that's > >the problem. I'll check the other things when I get back into town [quoted text clipped - 10 lines] > > R. I replaced the factory prop with a plastic one of the same pitch. Mike > Factory prop or did you change it for one with a different pitch? > [quoted text clipped - 12 lines] >> >>R. I had a similar problem on a different engine the weekend before last. I had to keep pumping the bulb to limp back to port. The problem was the fuel pump. An $11 rebuilt kit fixed the problem. Tom > Hi everyone, > With the wealth of knowledge and experience here, I have a problem that [quoted text clipped - 19 lines] > Thanks, and fair winds, > Mike >My (new to me) Yamaha 9.9 HP outboard (built year 2000) usually runs >fine at lower RPM, but when I ramp up over 35% of max speed the engine >will invariably run fine for 20-40 seconds and then cough, sputter, slow >for a few seconds and then speed back up. The faster the RPM, the more >frequent the problem. Could be a partially blocked jet in the carb. Thank you, everyone! The problem was a plugged vent- I got it cleared last night and ran it smoothly for 15 minutes. Mike > Hi everyone, > With the wealth of knowledge and experience here, I have a problem that [quoted text clipped - 19 lines] > Thanks, and fair winds, > Mike >Thank you, everyone! The problem was a plugged vent- I got it cleared >last night and ran it smoothly for 15 minutes. It'll be truly fixed when you can run it for 15 NM in short chop. That loosens the flakes and debris nicely, I find <G> R. Ah, if you are a pessimist you are never disappointed. I write that with the utmost respect, Rhys, because I have experienced it too many times in practice. After 7 NM with moderate waves I got the problem back again. After much more troubleshooting I found that I have a tiny oil leak somewhere. Turns out the Yamaha 9.9 is designed to drop to low RPM's and run rough when it senses a loss of oil pressure. After running at low RPM for a short while enough oil was accumulating in the reservoir to allow oil pressure to go back to normal, thus the intermittent nature of the problem. A quart of oil and 10 NM later the "effect" seems to be gone, although I still have to find the leak causing the problem. Mike >>Thank you, everyone! The problem was a plugged vent- I got it cleared >>last night and ran it smoothly for 15 minutes. [quoted text clipped - 3 lines] > > R. >A quart of oil and 10 NM later the "effect" seems to be gone, although I >still have to find the leak causing the problem. Interesting. Does it leak at rest or only when under load? What I am getting at is does the rising engine heat cause a gasket somewhere to fail, or is it the rising oil pressure that forces oil past a hole or gasket or crack or something that "closes" or reseats itself when the motor cools down? I'm glad you are getting closer to the ultimate problem, which isn't fuel, it seems. Believe it or not, that's a good thing <G> R. It is leaking at rest. When not running I keep it locked in the up position and out of the water. When I put the motor down and into the water I have found a small amount of oil comes out of a timy breather hole in the upper case of the motor. I haven't had the motor in the down position long enough to determine whether it also leaks when running. My plan is to identify where the at-rest leak(s) is/are occuring, repair it/them and then look for evidence of running leaks. It'll be slow, but I know I'm making progress. Thanks, Mike > Interesting. Does it leak at rest or only when under load? What I am > getting at is does the rising engine heat cause a gasket somewhere to [quoted text clipped - 6 lines] > > R. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.