Slow acceleration

[Murphyamaha]

My 15 hp 2 stroke is slow to come up to full throttle when fully accelerated in the water…. Week power. The response from the throttle is very slow when navigating at the dock, reverse and forward. Engine is not sputtering, it is running smoothly. When out of the water the engines responds normally with the throttle.

 

[racerone]

Sound like it is running on 1 cylinder.-----Test compression and spark first.----Out of the water it will sound just wonderful on 1 cylinder.----Simply because there is no load on the prop.

 

[Murphyamaha]

Sound like it is running on 1 cylinder.-----Test compression and spark first.----Out of the water it will sound just wonderful on 1 cylinder.----Simply because there is no load on the prop.

You are correct. One of the pistons does not fire alone, the other one will and motor runs. The one that isn’t running has spark. So why no power in that cylinder?

 

[racerone]

Bad sparkplug ?----Post actual compression values.----Could be a reed valve issue.

 

[Murphyamaha]

the fuel pump was leaking into the lower cylinder, flooding it. Took the pump apart and there was a tear in the membrane. Replacing the pump. Thanks for your help.