Yamaha 40HP 2 stroke to 50 HP?

[Graham Anderson]

I live in Canada and have a Yamaha 40 two stroke which weighed 153 lbs +/-.(without trim and tilt)

This same identical motor was available in the US at 50 HP. I had talked to one of the dealers in Montana about this and he wasn't really sure if I could convert mine to 50 HP. He thought maybe some carb jetting and maybe some electronic change, but didn't really give me the confidence that he was exactly sure.

I now heard there was some exhaust restrictor from another source but they were passing along some second hand knowledge.

I do have a Tohatsu that had an intake manifold restrictor that lessened the Hp from the factory and can be boosted just by taking the restrictor out.

If anyone knows what is involved in boosting the 40 HP to a 50 HP, I would sure be glad to know it. I would like to keep the Yamaha as long as possible because of the high HP/wt.

Thanks for any and all ideas.
Graham Anderson

 

[deejaycee_2000]

Re: Yamaha 40HP 2 stroke to 50 HP?

I can assure you that the 40hp yam don't have the restrictor plate or gasket like the 25hp tohatsu that you can take out and replace with the 30hp tohatsu to make it 30hp ...... the 40hp yamaha would need to be rejetted, reed valves changed, ports changed, exhaust changed to get 50hp out of it, it is not worth all the effort at the end ......

 

[Graham Anderson]

Re: Yamaha 40HP 2 stroke to 50 HP?

Thanks, that does sound a little more realistic, and I think I will just keep my eyes open for a low hour 50 and change the jet leg.
Graham