Yamaha F15C to 20hp (Serial number: 6AGK 1037798)

[hydro17]

Hello,
Last year I bought a 14ft Buster fishing boat with a Yamaha F15C (Serial number: 6AGK 1037798) for the small waters. The boat and motor are 2015.
I have now bought an ultrasonic cleaner and will rebuild the carburetor with a service kit. Looking in both the Yamaha parts catalogue and the Service and repair manual for the F15C/F20B the only differences between the 15hp and the 20hp seems to be the Jets for:

F15C Jet(#38) 6AH-14948-02-00/ Main Jet(#80) 676-14943-19-00/Plunger spring 65W-14335-00-00
F20B Jet(#45) 676-14948-05-00/ Main Jet(#112) 65W-14943-29-00/Plunger spring 6AH-14335-00-00


What have I missed? Is there a restriction somewhere? Would it be possible to increase the power up by 5hp by simple means?


IMG_1723.jpg

[yam911]

The carburetor part numbers are different. Is that because of the jets or is it due to some other reason?

I am having a hard time believing that it is just a jet change. Adding only more fuel will not result in more HP. If anything, less HP.

[hydro17]

Yes, you are correct. More fuel is not the answer...

I have now found that also the jet needle are different between the carburetors (2.2 vs 2.4) so it is probably not only the parts listed in my previous post that are different but the carburetor, which makes sense. The carburetor is the restriction not the intake or the exhaust. I even looked at the camshaft and they are the same.
I will research this further and also see if I want to spend $80 for a rebuild kit or $430 for a new F20 carburetor...

EDIT: Ok, so I found a new OEM carburetor for the 20hp motor on the internet and it fits/converts my 15hp engine to a 20hp. it is even cheaper than the rebuild kit. Who would have thought... So I will go down this route. Thanks!