Yamaha Outboard 'slipping'

syfuga

syfuga

Well-Known Member
Joined
21 Mar 2005
Messages
310
Location
Back in UK waters
www.syfuga.co.uk
Yamaha Outboard \'slipping\'

My 8HP Yamaha has just developed a fault. As you apply throttle, the boat picks up speed and all is well, until suddenly the engine revs rise and the boat goes nowhere.. its a bit like a car clutch slipping on a slope. Trouble is I don't know enough about the innards to know where to look. Is it internal, or is it the propeller slipping?
 
Re: Yamaha Outboard \'slipping\'

I had exactly the same problem earlier this season with the same engine and the culprit turned out to be the prop. Instead of a shear pin it has a rubber insert in it between the part that slides onto the drive shaft and the part holding the propellor baldes that is desined to fail to protect the engine. you can check this with the engine stopped by but putting the engine into gear holding the fly wheel still with one hand and trying to rotate the blades of the prop with the other hand, the blades should move. A new or refurished prop is in order. However a temporary fix is to screw some thin screws into the rubber area, parallel to the prop shaft, you'll see this when you take the prop off by removing the split pin and nut.
I worked out that snagging a line earlier in the season had caused this rubber to fail, but it only became apparent when I put the prop under load.
 
Re: Yamaha Outboard \'slipping\'

If it's like my ancient 8hp Yamaha 2T it has a rubber bush between the prop and shaft (instead of a shear pin) which is intended to absorb any shock loads. I'd look there first. Mine looked like this when I got it off.

DSC_0081.jpg


A new prop was the solution in my case - about £90 last year if memory serves.
 
Re: Yamaha Outboard \'slipping\'

Hey, that's interesting.

I have a 9.9 Yamaha, and the same happens with me at higher revs. Since I can get to hull speed before this happened, I assumed that it was the prop cavitating/aerating & /or stalling when I tried to drive it to do the impossible and get past hull speed. More evidence for this was that this happens earlier with a fouled prop.

My prop is well old too, didn't know that rubber bit provides the link between the splines and the blades.

Will have to check
 
You must log in or register to reply here.

Share this page

Top