Motorbike engine

PabloPicasso

PabloPicasso

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How about using a Japanese air cooled motorcycle engine in a boat. Loads of power, reliable, no water cooling probs or sea clocks or heat exchangers to screw things up. Light weight and plenty plenty power. Would have to be petrol though.

Would lower torque rating maybe be a problem. Certainly lots of horse powers
 
PabloPicasso said:
How about using a Japanese air cooled motorcycle engine in a boat. Loads of power, reliable, no water cooling probs or sea clocks or heat exchangers to screw things up. Light weight and plenty plenty power. Would have to be petrol though.

Would lower torque rating maybe be a problem. Certainly lots of horse powers
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How are you going to supply air to the cooling fins ?
 
Cooling fins? They're almost all watercooled nowadays. But who wants a 10,000rpm engine in a boat? In a racing speedboat perhaps.
Don't think all those electronics would like the salty environment either.
 
Hot exhaust is a problem as well as engine cooling. There used to be an inboard 'outboard' made which I seem to remember was basically a Honda BF10 mounted in a bed that could be fitted to the hull of a boat like a saildrive. Not seen it for a long time though. Petrol inside was the problem I expect.
 
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MASH said:
Cooling fins? They're almost all watercooled nowadays. But who wants a 10,000rpm engine in a boat? In a racing speedboat perhaps.
Don't think all those electronics would like the salty environment either.
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Yes, usually have both, the OP specifically said "How about using a Japanese air cooled motorcycle engine".
Anyway moot point, you still need the airflow to the radiator which you won't get at < 6 knots.
 
AngusMcDoon said:
Hot exhaust is a problem as well as engine cooling. There used to be an inboard 'outboard' made which I seem to remember was basically a Honda BF10 mounted in a bed that could be fitted to the hull of a boat like a saildrive. Not seen it for a long time though. Petrol inside was the problem I expect.
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You're probably thinking of the Saildrive 330. Now uses a Parsun engine and not that cheap either.
http://saildrive.se/
 
So the use of the low engine hours B&S I/C engine ( Cast iron cylinder bore ) from my 1998 or 1999 lawnmower is not a good idea? The deck of the (expensive at the time ) Hayter mower it came off rusted away like that of 1970s Lancia car on speed . Seems as if the engine was really designed to be used for something else after the Hayter deck, the temporary packaging, crumbled away. For me, it was a shocking revelation of how bad British products could be. The mild steel deck had no surface preparation coating, no primer and the thinnest coating of brittle paint imaginable.
 
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Many attempts in the past using B&S and before that Villiers small aircooled engines for boats. All failed miserably. Noisy, difficult to keep cool, petrol driven, needed large reduction ratios to reduce shaft speed, but few gearboxes suitable. Others have tried more sophisticated aircooled engines such as JLO, but always the same problems of too high revs, noise and cooling. More modern M/C engines will be even worse with high revs that need to be brought down to shafts speeds of below 1500rpm to turn big enough props to propel displacement speed boats. Possible with outboards on higher speed craft where you can have shaft speeds of around 3000 so 2:1 reduction works. However as those who use such engines as sailboat auxilliaries know, they are not good at low speed moving heavy displacement boats. Most of this type of engine, although sharing basic design with aircooled engines are usually watercooled for quietness and ease of temperature control.

There is a tendency to forget that it is not the engine that moves the boat, but the propeller, and you need a large slow turning prop for moving displacement boats. Those who have used old style Seagull Century Plus type engines will appreciate what can be achieved with a big reduction (4:1) giving slow shaft speed (under 1000 rpm), a big fine pitch prop, but very little HP turning it.
 
Another problem is that road engines and machinery engines rarely operate under full load. If you mow long wet grass your B&S motor soon gets distressed with the overheating.
Boat engines do operate under full load. You can't feather the throttle to cruise. You will just slow down.
 
Lakesailor said:
Another problem is that road engines and machinery engines rarely operate under full load. If you mow long wet grass your B&S motor soon gets distressed with the overheating.
Boat engines do operate under full load. You can't feather the throttle to cruise. You will just slow down.
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A trials bike air cooled engine would be perfect, designed with massive cooling fins for slow forward speeds, lots of torque at low revs, lightweight.....fit to boat transom with one of those Asian long tube setups they use in Thailand.
 
Possibly, but they operate for a couple of minutes under load and then rest. It may be worth trying with a big pitch prop to get boat speed at lowish revs.
 
I did long a go see a 27ft keel boat with a Honda stationary engine driving normal prop set up. Possibly it was just a stop gap until a diesel was fitted. He just used it for getting out of the mooring and I don't know how succesful it would be ona long motoring trip.
There are real reasons why many modern motor bike engines volkswagens and even some aircraft engines are fluid cooled. You can get a much more even contrrolled operating temperature which allows fine tolerances and so higher compression ratios. So there is a lot to be said for the indirectly cooled engine diesel or petrol. good luck olewill
 
20 years or so ago there was an Australian project for marinising Honda CX500 engines (transverse V-twin, pushrod, liquid-cooled). No idea what happened to it, though. I imagine it was fan-cooled to a radiator and, although less revvy than many Japanese bike engines, had to run some pretty giddy reduction gears.

For a while Royal Enfield (the Madras version) made a 6.5hp diesel motorcycle, claimed to do 200mpg. That might work in a boat, but on the other hand wasn't really a bike engine at all but a transplanted industrial lump. It vibrated like stink and deafened anyone within earshot, so no thanks.

So that leaves us with by far the largest application of bike engines in boats: wet bikes. The Yamaha VX Waverunner uses a modified R1 motorcyele engine: 1052cc, 4 cylinders, 20 valves and over 150bhp...perfect for leisurely chugging out of harbour.
 
Achieving a uniform cooling on a air cooled engine is a big problem. The cylinders at the "back" can get much hotter than the front cylinders and this causes excessive wear in the cylinder. Aircraft piston engines have this problem and the engines are covered with air ducted cowling which cover the engine and make it difficult to access or see any engine components without taking the ducts off which is a big job. Also the noise, which would be even louder than my Volvo MD11C; that is loud. The modern water cooled motorbikes are complex little engines, perhaps not robust and not simple enough for yachting purposes.
 
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