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Boat Forum / Building / March 2008VW Diesel conversion on Mercruiser I/O
Hello all, I have just purchased an older Starcraft 18' runabout that currently has a 120hp 4cyl Merc gas engine coupled to a series 120 Merc I/O drive. I intend to convert this package, using the I/O, to diesel using a 52hp 1.6L VW diesel engine in place of the merc 4 cyl. Due to the relative unavailability (and cost) of a wet exhaust, I intend to use a dry stack, and run the diesel with a radiator normally found in the VW vehicles...side mounted and all tucked into a rear engine box that will be manufactured to allow adequate breathing and heat dissipation. My question is regarding the pump system in the I/ O...can I just remove the impeller, or should I direct its output into an open circuit back into the bay? Does the pump in the I/O have any cooling or lubricating capacity for the unit? This project is intended to provide for a work boat used in Coos Bay, Oregon, for non commercial fishing and crabbing. Reliability and economy of use are considerations. >Hello all, > I have just purchased an older Starcraft 18' runabout that [quoted text clipped - 13 lines] >Oregon, for non commercial fishing and crabbing. Reliability and >economy of use are considerations. Many years ago the lobstermen on the Maine coast used automobile engines in their boats. They used a "keel cooler" consisting of several lengths of galvanized pipe. the system was fresh water only and used the original auto water pump. Even used anti-freeze in the winter time. A much more effective system then a radiator. After all if you have the whole ocean to cool the engine why use a less efficient medium? Bruce-in-Bangkok (correct email address for reply) I have no idea what tree you have been living in, but your idea makes no sense. In the first place wet exhaust manifolds for the VW diesel are readily available from Pathfinder Engines and others. The modern VW diesel makes in excess of 100 HP, not 52. Dry exhausts are a real fire hazard and an unecessary risk. Keel cooling is a very good idea and is more common in fresh water than salt, however you will still require a 5 liter or so expansion tank. Steve > Hello all, > I have just purchased an older Starcraft 18' runabout that [quoted text clipped - 13 lines] > Oregon, for non commercial fishing and crabbing. Reliability and > economy of use are considerations. > I have no idea what tree you have been living in, but your idea makes no > sense. In the first place wet exhaust manifolds for the VW diesel are [quoted text clipped - 28 lines] > > - Show quoted text - Well, Steve, the tree I live in is the one behind my machine shop. The reason that I will not put a wet stack on the boat does, in part, involve the 488 pounds that the British Company sells them for (I don't know how much that is in real money, but suspect it is in excess of $1000US). Secondly, I have a few of the 1.6L diesels in my inventory, and as I will not water ski behind the boat, I think 52hp is adequate to my task, and more reliable and fuel efficient to boot (I've rebuilt ten of these little engines in the past 5 years)...In fact, if I had one of the newer diesels available to me, I would still use the 52hp model. As the boat (18' open runabout, aluminum hull) will be both trailered and occasionally beached on sand bars, and as I don't want to pierce the hull or transom to build a cooling system, the close-coupled radiator system mounted on the injector pump side of the motor looks like a viable method, and the system's entire footprint will be less than 32" wide....Oh, did I mention that this was to be a work boat? What I am looking for is reliability, safety and fuel efficiency...speed, resale value, and the approbation of the boating community are not issues. On Mar 5, 3:53 pm, elysianfi...@earthlink.net wrote: > Well, Steve, the tree I live in is the one behind my machine shop. > The reason that I will not put a wet stack on the boat does, in part, [quoted text clipped - 15 lines] > efficiency...speed, resale value, and the approbation of the boating > community are not issues. He probably means the VW TDI engines, which need a computer to run, and provide much less that 100HP on marine applications, (@2750 RPM, aprox.). I googled 'vw wet exhaust', and here is a link to a wet exhaust you could use for much less weight and cost that you state: http://www.frenchmarine.com/Content.aspx?Content=9 Embedded are links to particular products and also to VW's SDI engines (I guess they are direct injection, not computer needed). The reason I mention the computer is that is a really bad idea to have essential electronics that close to salt water. >Well, Steve, the tree I live in is the one behind my machine shop. >The reason that I will not put a wet stack on the boat does, in part, [quoted text clipped - 15 lines] >efficiency...speed, resale value, and the approbation of the boating >community are not issues. For what it is worth: Nearly all of the commercial fishing boats here are powered using a large truck engine - say 200+ H.P. equipped with a marine gearbox. Cooling is through a sea water to fresh water heat exchanger using a centrifugal pump (mounted below the water line) to circulate seawater and the normal engine cooling pump for the freshwater side. Used seawater is vented overboard. The standard exhaust manifold is used connected to a vertical hot exhaust which normally has a wire mesh protector. I mention this because fishing boats usually are fitted out using the cheapest method that works and none of them use a radiator... Having said that we did have three oil production barges in the Java Sea and the generator sets used radiators. As these units were oriented with the radiators pointing outboard and the fans blowing out they worked pretty well but a radiator does put out a large amount of hot air. So... your idea will work but for whatever reason people that use boats for a living do not to it that way. In closing, it is pretty easy for any competent welder to make a water cooled exhaust manifold. Bruce-in-Bangkok (correct email address for reply) > On Wed, 5 Mar 2008 09:53:22 -0800 (PST), elysianfi...@earthlink.net > wrote: [quoted text clipped - 48 lines] > Bruce-in-Bangkok > (correct email address for reply) It really doesnt take a competent welder to make a water cooled exhaust, just some time and some pipe. That said, the shrimpers around here often run a hot dry exhaust with no mufler...much to my displeasure in the morning as they run by the house at 5AM and I am trying to sleep. But it does work fine and reliably. As to the cooling, the radiator idea really stinks. A heat exchanger is also something that can be manufactured in the garage, its not rocket science. The keel cooler however is the best idea and they are used extensively in the shrimping fleet. For a 52 HP diesel the size if the cooler is not excessive, probably a couple of 1.5" copper pipes 4' long would do the job. But I am not an marine engineer so dont take my word for the size. I have a 50 HP Volvo Turbo charged 3 cyl diesel in my 25' Albin and the heat exchanger is very small. I would adapt one from something else. Just do a search on EBay for "Heat exchanger" and look for one with a physical size and price that you like. On Mar 4, 6:58 pm, elysianfi...@earthlink.net wrote: > Hello all, > I have just purchased an older Starcraft 18' runabout that [quoted text clipped - 13 lines] > Oregon, for non commercial fishing and crabbing. Reliability and > economy of use are considerations. I don't think that the cooling circuit has any impact on the lower unit. I'll check with the Mercury dealer here tomorrow and repost. |
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