Questions for 2-stroke experts

Sometimes they offer a range of HP per engine Like a Johnson V-4 they were 85- 140 hp. The 85 HP was 93 CI and the 115 and

140 were 99 CI. The motors are very much the same but had different porting, heads, carbs, exhaust tuning. If you are luck many be a 2 or 3 HP shares most of what yours does if no sell and buy what you want. I have rebuilt many outboards much bigger than what you have but, its the same idea. Trying to make them perform better than new will cost more than just selling the one you have and buying what you want.

Sorry, but your goals are incompatible. I'm not a two-stroke "expert", but have enough knowledge to understand how these things are tuned. Just about the only thing that can produce your desired result is a larger displacement engine. A supercharger will blow most of the extra charge out the exhaust port, especially with a tuned chamber to pump some of it back into the cylinder.

Bill

Eric R Snow wrote:

====== Larger valves and a high-lift cam ought to do it. :-)

Gearbox reduction??? Ken.

That is easily done. Just change the fuel to 30%nitro 60% methanol 10% bean oil drill the jets out to about twice there normal size and off you go!

Charlie

You cannot have it both ways. You will have to choose either low rpm/flat torque curve or high rpm steep torque curve. Changing the size of the flywheel does nothing other than smooth things out. Two stroke engines are inherently narrow power band designs. If you could double the output of an engine without changing carburetion then you are truly a miracle worker. Randy

Basically, your goals are incompatible. You could develop more low RPM torque, allowing you to idle down to a lower RPM, by lowering the ports and reducing their size. You could develop more top end HP by raising the ports and increasing their size. Since you can't do both, you have to choose one or the other.

Simply changing the flywheel weight doesn't increase low end torque. It just smooths out any transient loads applied to the engine. So that won't do anything for you in an outboard motor situation where the prop load is relatively steady at any given RPM.

A more feasible option would be to bore and stroke the engine for greater displacement, which would give you more torque across the RPM range, allowing a lower idle, and increasing high RPM HP. But I doubt you can bore and stroke it enough to double its HP unless you also make intake and exhaust changes.

You could also try to supercharge the engine, cramming more air and fuel into the same size cylinder. Or you could use nitrous injection, or nitromethane fuel, to get more bang out of the existing engine. The danger there is that if you don't know exactly what you're doing, you may get a bigger bang than you intended, a destructive bang.

Your best course is to simply buy a bigger engine which has the characteristics that you want.

Gary

Back in the late '40s someone gave Grandad a single cylinder Muncey Neptune. The only way to troll with it was to place a large sheet metal disk ahead of the prop to effectively reducing the prop size.

Gerry :-)} London, Canada

Like in the gas powered weed whacker I bought for two bucks because it was leaking oil. Gerry :-)} London, Canada

Simple solution,

Use a centrifugal vari-pitch prop!

Yours,

Doug Goncz ( ftp://users.aol.com/DGoncz/ )

Read about my physics project at NVCC:

plus "bicycle", "fluorescent", "inverter", "flywheel", "ultracapacitor", etc. in the search box