small or bigger counterweights?

[yukoner]

I'm building a motor from various parts form several 50 h.p. Yamaha's. I have two different cranks. One is older I think,it has smaller counterweights. Is there an advantage using it over the other with obviously more rotating mass? Common sense tells me less weight would be easier to turn and faster.

[Fast Fred]

the smaller one, says 400 on the rods, mostly found in 40hp.

[yukoner]

So is that a yes the smaller is better?

[David Mason]

Do you want more RPM's ? In very basic form, the smaller one will give you more acceleration and the heavier will give you more top end. Of course this depends a lot on what else you do to it.

[yukoner]

I'd like to keep it stock. Maybe slight port work. Don't want to do too much with them tho, $5.25 gallon gas here. Are there better carbs from different years?

[Tomtall]

Gibert - This is how I would look at it. First - What size boat are you running this on? Is it a small displacment hull that is light in weight? or is it a larger hull that weighs quit a bit? Do you want the engine to carry it's RPM when the engine is being put under load? such as going thru a corner. Or do you want snappy throttle response and good acceleration comming out of the corners? Are you going to port the motor to be peeky on RPM or have a wide RPM range. All these things can help you make your decission on the internal parts you use. More crank counterweight will make the engine carry it's RPM for a longer period were as the lighter throw crank will punch faster and decell quicker.Same is true with your flywheel choice.Bigger is not always better on carb's.Your engine can only pump so much air. By going bigger it could kill your bottom end.If you have access to a boat junk yard and can search their pills of carbs you may find a match with larger venturies. Sounds like a fun project. Good luck!