90hp merc revving up on its own once at 1/2 throttle

[Brad250]

First time out this year and everything ran fine until about 8 min into cruising and the 89 2 stroke 90hp started to rev up higher on its own while in gear but not increase speed. Like it was a clutch slipping. Then I noticed that water wasn't pissing out of the eye at the back. I un clogged that and the problem still persisted. What might this be?
I limped back to the launch no problem at a low speed but not sure where to start on this? Runs and idles great, this problem is one over never had so I'm lost

 

[jhow0228]

Re: 90hp merc revving up on its own once at 1/2 throttle

Spun hub?

 

[jhow0228]

Re: 90hp merc revving up on its own once at 1/2 throttle

Had the same issue in my friend's boat. Was running at WOT and the boat just quit moving. The hub had broken loose from the prop so everything was still spinning but the prop itself. We were also able to limp back to the ramp at low speed it would still connect enough to turn the prop.

 

[Brad250]

Re: 90hp merc revving up on its own once at 1/2 throttle

Ok that'll be the first thing I check in the morning thx

 

[jhow0228]

Re: 90hp merc revving up on its own once at 1/2 throttle

Did it start pissing after you unclogged it? If not, could be bigger issues since the impeller is on the drive shaft and you're motor is revving up and not going anywhere. If it started back, then you know at least the drive shaft is spinning.

 

[Brad250]

Re: 90hp merc revving up on its own once at 1/2 throttle

Ya once it was Unclogged it ran fine at slow speed still.

 

[jhow0228]

Re: 90hp merc revving up on its own once at 1/2 throttle

I'm almost positive it's a spun hub then. Luckily, not too expensive to repair. If it was any other problem, there would have been other noises with it(grinding, popping, or clanking). Best thing to do is take the prop off, hub will come off with it, and take to a local prop shop and have them check it out. You're not going to be able to apply the same amount of torque by hand to cause it to slip.

 

[Brad250]

Re: 90hp merc revving up on its own once at 1/2 throttle

Pulled it off today and it looked like it could Definatly be the problem. I already had a new prop and so I installed it. Try it out this weekend

 

[jhow0228]

Re: 90hp merc revving up on its own once at 1/2 throttle

Glad to hear that it might just be the hub. Post again after you've ran it and let it us know if that was the issue.