Yammy 15hp upgrade

[jpj2424]

Hi. Im new to the forum and would be very greatful if someone could give me some advice. I've purchased a set of Boysen performance reed valves for my Yammy 15hp 2stroke 2009 and wondered if I could fit a new carb from a 20hp 2stroke? Is the carb compatible and would doing these 2 mods be sensible in order to give me a justifiable power increase.

If so, does anyone know the part number for the carb I would require. Many many thanks in advance.... jj

[Fenlander]

Hi and welcome to the forum.

It is the Yamaha 9.9 and 15 2-strokes that are cross compatible. The 20hp 2-stroke was a 50% greater cc and just not the same motor.

The 15hp is a great outboard and I'd just make sure that was serviced perfectly then make sure its setup on the SIB is perfect inc rev counter testing to ensure best prop pitch is fitted and finally minimise weight carried.

[jpj2424]

Hi and thanks for the reply. As I understand it the 20hp engine as u say has bigger cylinders but I was thinking the carb is the same fitting as the 15hp but has a bigger throat to it? I can only hope lol?... jj

[jpj2424]

Yep. They sure r great outboards and I'm happy with its performance and reliability. I service it regularly it's mint. 2up with baggage I get 19/20mph. Would just like to squeeze as much power out of it as poss. Many thanks.... jj