Yamaha 40 & 50HP same block?

[thelightning]

Hello,

I am looking for a 40 or 50 HP for my new spitfire.

I found a nice looking 40HP Yamaha, now as far as i understand the 40 is made of the same powerhead as a 50HP Yamaha.
Now i would really like a 50HP if it turns out the prop i will buy is a bit too heavy for 40HP.

The dealer told me he can do it for over 300bucks cuz he would have to replace the exhaust and seals or something, i dont really believe him.

Do u guys have any idea what is the exact diffrence between the 2 engines and how to make the 40 a 50 or tune it up a little any other way?

Thanks

 

[tashasdaddy]

Re: Yamaha 40 & 50HP same block?

go to the yamaha site, and look up the engine diagrams, parts list. most motors of different hp use same basis block, different bores, strokes, carbs, exhaust, porting. gearing.

 

[Silvertip]

Re: Yamaha 40 & 50HP same block?

Bore and stroke are the same but intake and exhaust parts, port and ignition timing probably are not. It's very easy for the factory to "build" the engine but it is generally not economically sound to do the conversion. Parts are simply to expensive unless you have another motor you can salvage parts from. The dealer may get you "almost" a 50, but if port timing is involved, you will not get a 50 and certainly not for 300 bucks.