15hp 4 stroke Yamaha compression

[Salacia]

Hi Folks

I recently picked up a four stroke 15hp 2006 Yamaha outboard and it seems to be lacking on power slightly. I have stripped the carb and cleaned etc. and compression tested both cylinders which are giving me 100 psi. Does anyone know if this is an acceptable reading and what they should be?

Thanks in advance

Rob

 

[robert graham]

Re: 15hp 4 stroke Yamaha compression

100lbs. On both cylinders is fine....if you're accustomed to a 2 stroke motor's power then the 4 stroke may feel and sound somewhat weaker, since they tend to be smoother and quieter.....

 

[JustJason]

Re: 15hp 4 stroke Yamaha compression

100 is a little low. Spec in the manual is 139 psi. (and really you should get higher than that) You should try a different gauge just to rule out the possibility of an inaccurate compression gauge

 

[Salacia]

Re: 15hp 4 stroke Yamaha compression

Thanks guys I will check it out with another gauge as this one is brand new and I haven't checked it on anything else.