Yamaha gears slipping

[hollyj2]

My 1998 Yamaha 9.9hp 4 stroke shortshaft with thrusting prop is operating ok up to about 1/3 revs. When I go above 1/3 the revs go up but the boat slows down. It only does it in forward. I'm guessing it is something in the gearbox. I recently replaced the water pump impeller (after which the motor operated fine. I have tried adjusting the gear linkage but it made no difference.<br />Any ideas would be appreciated.<br />Jason

 

[rodbolt]

Re: Yamaha gears slipping

hello<br /> I am guessing the prop hub is spun. if the gears were slipping your gear oil would look like liquid metal and soon after the first slip a lock up would usually occur.

 

[hollyj2]

Re: Yamaha gears slipping

Thankyou, I will have a close look at the hub,can you tell me what to look for and how to fix the problem?

 

[bigbrownbuku]

Re: Yamaha gears slipping

if you pull the prop and look at the back. there is a section of rubber between the spline and the base of the blades. sometimes it looks good but slips. a new prop for that engine is fairly cheap. a hub replacement might set you back half the cost of a new prop.

 

[hollyj2]

Re: Yamaha gears slipping

Thankyou Ben

 

[Trent]

Re: Yamaha gears slipping

Another easy check is to get a magic marker and mark across the prop hub. Go use it. If the marks move, Then you know the prop hub is spun.

 

[hollyj2]

Re: Yamaha gears slipping

Thank's Gent's, <br />A new prop had been ordered.