Lower unit chatter

[Yamauser]

Excuse me if I am rehashing an old question. I did a search and didn't see this question discussed. I am running a '02 Yamaha F115. I have noticed a chattering noise that seems to come from the lower unit when in forward gear at idle speed. The slightest increase in rpms stops the noise. I first noticed this about the time I switched to a Yamaha black stainless steel prop. Is this a sign of a problem in the lower unit or is it something common with the additional weight of the SS prop? Any help would be appreciated.

 

[andymach23]

Re: Lower unit chatter

Hi there,

This is normal and has been covered a few times. I noticed it on my F40 when I bought it and my dealer sent the lower unit back as a precaution. The new one did it as did a F100 that was in their yard for service.

Rodbolt has explained it really well in the past. In very basic terms, with the 4 stroke power set up, the gearbox or some part of the drive is always playing catch up with the crank at these low revs, when the prop isn't under load in the water. The SS prop has an effect also I think.

That's a rubbish explaination. If I can find Rodbolts post I'll add a link.

Cheers

Andy

 

[andymach23]

Re: Lower unit chatter

There you go...

http://forums.iboats.com/showthread.php?t=249361

There's link to Rodbolts explaination in this thread.

 

[rodbolt]

Re: Lower unit chatter

its rather normal, even worse if an untrained shop monkey didnt put the lock ring and collar back together correctly when a water pump is done.
my F150 was really bad with a 4 blade turbo ss prop. prop worked very well. the noise drove me nuts.
now i run a 3 blade black yamaha wheel and all is well. the other prop worked better just drove me nuts at idle.

 

[Yamauser]

Re: Lower unit chatter

Thanks for finding the links for me Andy, my search skills really suck. Thanks for your response Rodbolt, your old posts were a help too.