prop hub?

[muskie guy]

I have a 90 hp Johnson 4 stroke on a pontoon. When we put it in the water this week for the season it would run fine at a low to mid range rpm. When you give it full throttle the engine revs up like there is no load on it. Is it the prop hub or do I need to be looking for something else?

 

[AEROCOOK]

Easy enough to test, just mark the inner part of the hub and the prop in the same location then induce the rev condition. If the marks are no longer in the same location, your hub is spun.