Revving at High Speeds

[johnson115]

Just put the boat in the water for the first time this year. She started right up and ran great. After 2 or 3 minutes running at cruising speed, the engine started to rev up and then back to normal repeatedly. I tried increasing RPMs, but the problem followed. When I slowed down, the engine ran steady. I hopped up on plane again, and a minute later, the revving resumed.
I had the tank pumped last week, so I know there is good gas. I also replaced the fuel filter. My initial thought was the fuel pump, but I have also read that a spun prop hub bushing can produce the same symptoms. Any help with a step in the right direction is appreciated.

 

[Docksidemarineservices]

Welcome aboard!

Either your propeller hub has spun or your propeller is cavitating.

 

[johnson115]

Thanks for the reply. The prop shop stress tested the hub, and it was good. I'll pick up the prop Friday and test it out this weekend.

 

[racerone]

Mark the hub and the outside of the prop.-------------------If marks move than it is slipping.--------------Pick up a timing light and hook it up to see if it is a coil / sparkplug that is cutting out.