Evinrude 115 has no power at full throttle

[todd1962]

I have a 1978 Evinrude 115 Model 115899C. It starts and runs fine both in and out the water. Once in the water it only goes about 5 mph at full throttle. It shifts from forward to reverse with no problem. Just no power at full throttle. Did a compression check when I got home and all 4 cylinders show ~100-110 psi. Not an overheating problem because it's pumping water good.

What do I need to look for as the problem?
Thanks
Todd

 

[racerone]

Compression is low.------But it sounds like you do not have proper spark on all 4 leads.----Is the timer base rotating ?----How did it run for you last week ??----Was this a sudden failure ?----I would pull the 4 bypass covers ( 6 screws each ) to look at pistons / rings.----Could be a ruptured diaphragm in fuel pump too.----Or sheared flywheel key.----Bad float valve in 1 carburetor ?-----Some simple trouble shooting will quickly determine where the problem is.