possible to upgrade 1992 115hp v4 to 140hp v4?

[aeomholt]

By reading I've seen that the Yamaha 115-140hp V4 have the same engine displacement (1730cc). Does anyone know if its possible to upgrade the 115 hp to the bigger 140hp and if it is, what have to be replaced? This is a two stroke engine so it cant be that much difference [img]smile.gif[/img] The 9.9hp can be upgraded to 15hp very easy so why not the 115? hehe

[getyouten]

the ports in the cylinder is the difference.

[aeomholt]

does this require grinding or is it a part that can be changed easy? what about the exhaust/intake/intakevalves/carburettor jetting? do you have any sites about this?

[Ken]

aeomholt,
I was hoping someone with personal experience would answer your post - I've never tried it, and I have a Yamaha C115 V-4 myself. I can speculate that in addition to bigger ports in the cylinder walls, gonna have to go to larger high speed jets, maybe stronger connecting rods, and ignition timing may be different also.
I am going to refer you to a fellow down in Florida who is the most knowledgeable person I know (on any of the forums I belong to) when it comes to squeezing out more hp from the Yamaha motors. Go over to www.maverickboats.com and look up "Hamfisted" and PM him. Hopefully he can answer your questions.
Good luck [img]smile.gif[/img] ,
Ken K

[aeomholt]

Thanks Ken! [img]smile.gif[/img]