So i have a a zenoah g260pum and a g230 (car engine) and i am not sure which one to use in a race tomorrow i believe they are very different engines. but i cannot find unloaded rpm for the g260 and i am wondering which one will go faster with the same prop and if the slower one has more torque allowing me to put a bigger prop on it.

I am not sure but all i know is that the 230's unloaded rpm without pipe is 19500

Thank you very much for the help.

It seems the 26 cc zenoah engine would turn slower and produce more torque than a smaller brother 23 cc.

So the g230 would be faster than the 260 with the same prop or would the g230 not have enough torque to reach a high rpm?

Among a lot of other factors, I think that answer would depend on the size and pitches of the props.

If the 230 can turn the same size and pitch prop faster then it would be faster but it seems there would be a point that increasingly larger and higher pitched props would not be turned faster by the 230. To find that point I think testing is in order.

??? need to know what hull design it's going into??

I just have to ask out of curiosity. Why?

If the motors are going in the same boat it will be somewhat negligible. The only way I see the hull playing any part in this is its size (displacement) in relation to the thrust cone of the prop. Typically the larger prop would be better on a larger boat. I hope we all know what happens when you put a prop on a boat thats too big for the boat. Torque Roll!

should have said what size of hull , first off and hull design second. better.

A jersey skiff 50"

Thank you for all of the answers

-Ben

Ben,
Without wearing you out with all the technical reasons why one engine is better then the other I will give you my opinion. The 260PUM is a marine engine and more suited to what you are looking to do. There are more parts available to help you mount it in the boat and more props available to suit the power characteristics of that engine. The G230 is a air cooled engine and is more suited for RC Cars and GoPeds. It is not really a hard choice when you consider that you already have a more powerful marine based engine at your disposal.

Good Luck
Carlo

In the boat you would want the marine engine no doubt for obvious reasons. The G260PUM is watercooled that is reason enough.
Pull more prop easier and surely be easier to setup and tune.