125 Force revs of nowhere

[stixx]

Hi, (I'm new'ish to boating) I have a 125 on a 1986 bayliner. Sometimes while I am driving, the engine revs up like crazy and the motor seems to "jump up". It's pretty loud
Could this be due to the trim/tilt motors etc not keeping the motor in place ? Or could it be a weak transom??
I am waiting for the T&T parts to come in to change them. The motor falls on its own and doesn't easily trim/tilt.

Thanks

 

[Nordin]

Sounds like a spun prop hub or a bad cluchdog maybe a not right adjusted gearlinkage.

 

[stixx]

Ha...Um..I can ask my mechanic what that means. Thanks for the input.

 

[SkiDad]

Spun prop. Happened to me.

 

[stixx]

Ski Dad. If I change my prop should that help ?

 

[Jiggz]

Don't just change without investigating. The least you can do is to mark or score the inner and outer hubs with a straight line or dots. Do a test and if the line or dots is not aligned after a quick run, then you know it is spun.

But if the scored line or dots stay aligned, then you most likely have slipping clutch dog. Which you can easily fix by biasing the forward shift gear. Unless, this was already done before and then the clutch dogs needs to be replaced or repaired.

 

[stixx]

I'll take it for a ride today. Thanks. This helps alot.

 

[stixx]

I had a family member look at the prop and he said it was faulty. He changed it for me and I'm going out shortly to try it out.
Thanks everyone you helped to diagnose the issue

Stixx

 

[stixx]

I went out for a ride today. At first it seemed worse but it eventually got better. It still doesn't seem to be 100 percent. If it's not the prop, any other ideas ??
Thanks

 

[SkiDad]

Sorry for bad advice. I should have said more but was on a cell phone. Did you mark a line across the hub like Jiggz mentioned ?

Is the loudness you metioned a loud thud or the loudness of the engine racing ?