Yamaha 15hp -> 20hp

[Pim]

Hi All,

Been searching on some tech info on my recently purchased 2007 Yamaha F15.
From what I can see. The 20hp is the exact same motor.

Found out some differences in carb jetting. But from my knowledge air needs to be added to compensate for the richer mixture. In order to achieve larger hp.

Is there any knowledge on this form regarding this topic?

In my opinion, either the exhaust needs to be opened up or the camshaft is different. Since carb and intake mani are exactly the same.

Regards, Pim

[Poly]

Originally Posted by Pim

Hi All,

Been searching on some tech info on my recently purchased 2007 Yamaha F15.
From what I can see. The 20hp is the exact same motor.

Found out some differences in carb jetting. But from my knowledge air needs to be added to compensate for the richer mixture. In order to achieve larger hp.

Is there any knowledge on this form regarding this topic?

In my opinion, either the exhaust needs to be opened up or the camshaft is different. Since carb and intake mani are exactly the same.

Regards, Pim

You probably need to take the full parts list for both engines to compare. On a yam 2 stroke 20-25 was the same except for the carb and the exhaust, all other part numbers identical. I think there were some timing differences too.

[Davie]

Assuming your engine is an F15C and your trying to make it a F20B. I tried this as I have one that had botched carb. It wont run. Altough both engines advance the ignition to 30 degrees the advance curve is very different the engine now has a massive flat spot. The CDI unit is different part. I will gladly swap you carbs.... Nothing ventured nothing gained. Fail.

VERDICT= FAIL

[Pim]

Ok, so with a F20b CDI it would??

What did you change?

[Davie]

yes but there about £600.