I've found a 50, but it's out of my price range considering the amount i'm spending on the refit on the rest of the boat to make it support a bit more power. I've not been able to find a good 60 or 70. Rather annoyingly my boat used to have an old yamaha 60, but my uncle pulled a switcharoo. i'm not too jealous though, i've seen his fuel bills. Also what's the best prop?

Have a look at what rolfhat did with the 3 cylinder 850cc block.

I gave loads of bits to beamish ken on here. Forget upgrading the 40 to a 50 it will be faster but try find a 50 g which runs the 850cc power head or find a 60 or a 70. Boat will take the power no problem as long as you have the transom supports. Your problem will be finding insurance

Hi I understand you're the man to talk to with regard to yamaha parts. I've got a 40veto that could do with a bit of a boost, as the rest of my family are going faster and faster and i can't keep up. Do you know what paarts i would need for a significant power boost? is the exhaust manifold not strictly necessary as it's going to be an expensive PITA to swap i assume, like all exhaust manifolds.
Also do you have any tips on propping it? I don't know what prop it's running right now, but whats the sweet spot for these engines on an sr4?

Please pm me