motorcycle engins

[gert]

can a 500cc two cylinder four stroke water cooled kawasaki motor be converted to marine use?

[Russ]

Strictly an opinion but I wouldn't think so.

First the engine is mostly aluminum and probably wouldn't stand up to salt water for very long. Second, I don't think an engine like that develops enough torque to swing a large enough prop to move a boat of any size. Although I could very easily be all wrong.

Besides how would you attach the handlebars to the rudder?

[Donn]

http://www.smallboatforum.com/SBF%20Image%20File/engine.jpg

"The above 'foto' is of a 2-cylinder horizontally opposed, four-stroke inboard with an overall height of 17.5", weighing in at 290 lbs., 142 cid. 4250 rpm produces 84 hp--and from 700 rpm through 4250 rpm--it produces 130+ foot pounds of stump pulling torque. It's called the "Montana Troller". This might be the closest thing to a motorcycle engine, maybe an older BMW, but water cooled...

This marine inboard low end torque puller was developed by Bruce Hanson, somewhere in Montana,USA and shown at the Chicago IMTEC (Marine Trades Exhibit & Conference) Show in 1998. Haven't heard a word since..."

Small Boat Forum (http://www.myasylum.com/sbf/messages/142.html)

[Wayne Jeffers]

Years ago, someone (Clark Craft?) offered plans for a couple of little hydroplanes intended to be powered by 250cc motorcycle engines.

I see no particular reason why a number of different motorcycle engines would not be well-suited to marine conversion.

As in the photo Donn posted, the opposed-cylinder configuration has the advantage of having a very low profile. In addition to BMW motorcycles, Honda Goldwings are 4-cylinder, 4-stroke, water-cooled engines in this configuration. BMW's and Goldwings are also shaft driven.

One downside, most motorcycles do not have a separate transmission. It's in the same casting as the engine and often shares the engine oil. They don't usually have a reverse gear.

I wouldn't worry too much about them being of cast aluminum. The Subaru engine featured in the WB conversion article a few years ago was also aluminum.

Whether conversion parts are easily available for motorcycle engines is another matter.

Wayne

[Donn]

Some of the earlier hydroplanes (1900-1930) were powered by motorcycle engines.

If I'm not mistaken, some of the newest PWC's are powered by aluminum block motorcycle engines, including 4 strokes.

It doesn't have to swing a wheel to power a boat. Jet pumps don't require torque, rather high revs.

[johnw]

Seems like it could work if you don't use raw water cooling and you could get the gearing right. One thing, the aluminum used in motorcycle engines can corrode to a surprising degree just from salt air, and sitting in the bilge could be bad for it. Also the electrics are not adapted to wet environments. Are you planning this for a speedboat that lives on a trailer, or for a boat that lives in the water?

[gert]

Just a little lake boat for the kids to anoy the ducks with.

[mmd]

The problem with most engines developed for highways rather than waterways is that they do not have sealed ignition and fuel systems. People keep putting them in enclosed spaces where gasoline fumes build up and then hit the ignition button and - KA-BOOM!! They work fine if you keep them out in the open air like they were designed for, JUST DON'T COVER THEM UP !! :rolleyes:

(Sorry about all the yelling, but it is a topic that I don't think is given enough importance in homebuilding.) redface.gif

[Wayne Jeffers]

Good point, mmd. Thanks.

To me, the phrase "marine conversion" means, first and foremost, converting the engine to minimize fuel vaporization potential and to eliminate all sources of open external sparks (ignition parts, alternator, solenoids, switches) which might set off any vapor in a closed compartment.

I would recommend the book Inboard Motor Installation, by Glen L. Witt and Ken Hankinson, as a reference for anyone contemplating converting any engine to use in a boat.

Wayne

[Henri]

My two cents worth - The Honda 500cc liquid cooled V-2 out of a CB or GL 500 is an outstanding choice for a marine engine, and it has a shaft output if you use the trans. Take off the two carbs and make a plenum intake manifold for one carb, make a 2 into 1 exhaust and you have an engine that will run all day on about 1/2 gal/hr. The 650cc V-2 is quite a bit shakier and not as smooth. On these 500cc engines, the weak point is the plastic cam drive chain tensioner

[Wayne Jeffers]

Originally posted by Henri:
. . . Take off the two carbs and make a plenum intake manifold for one carb, . . . Good point, Henri. We forgot to mention the part about balancing carbs on a one-carb-per-cylinder engine. :eek:

Wayne

[DesignByBird]

Gert,

As Donnwest correctly says many hydroplanes and light boats of the beginning of this century were using light petrol motorcar and motorcycle engines, indeed the first outboards were motorcycle engines fitted with a long straight shafts (similar to those still used in many parts of the world).

While I was living over there on the Chesapeake, I likewise wanted to build a lightweight (motorcycle motored) stepped hull inboard – to use the Goldwing 4cyl-boxer 100hp. water cooled unit. Redundancy and relocation put paid to those plans, but would have used a closed cooling circuit (complete with antifreeze) and heat exchanger plates through the hull or s.s. tubes along the hull (protected through their location alongside grounding strakes).

Having been a motorcyclist for most of my extended youth, I can assure anyone that the best of British weather, on salted roads, being blasted at the engine at 80+mph is a thorough testing to the ignition, wiring and systems. Jap. Engines tend to be lacquered or painted anyway. Engine revs are not a major problem with the existing gearbox and an appropriate pitch on the propeller.., keep it simple.. Electric start is nice. Throttle is easy to convert.., exhaust can use existing silencers / muffler – then pipe out through the transom.. (don’t change lengths or diameter too much before the silencer ; two strokes are particularly sensitive to back pressure, your four stroke less so.., but don’t go overboard !!).. Watch the (blue metal) heat from the manifolds – neither good for wood, FRP.., nor young fingers..

Precautions with petrol on a craft is essential, but can be sensibly achieved.., ensure earthing is generous... electronic (magnetic or optical) ignition helps a lot, as does changing from the metal to marine tight-fitting rubber spark plug caps and leads. And as mmd says keep it in the open / well vented (though that doesn’t mean exposed to the elements and spray).

Have fun.

[Gary Bergman]

Some motorcycles , such as my '51 panhead, indeed have separate trannies. Once had a rigid 1952 Triumph with separate tranny. combined engine/tranny unitconstruction do make o.k. morrings for small daysailers,just a pun,son.

[Sheep]

Having worked at a large motorcycle dlrshp for a number of years, I would not recommend a Honda V-twin such as their 500 of the late 70's/early 80's. That motor produced heavy vibration and was often seen back in the shop over the years.