Yamaha 8 transmission slipping

[Harry Usher]

I have a 2 year old Yanmaha 8HP Enduro. After using it for about 5 minutes at full revs in a planning RIB rubber dinghy, the prop starts slipping, the dinghy slows down and the engine revs high - the prop is still turning and driving the boat slowly. After a minute it's Ok again for only a short perioduntil it starts slipping again. Strange as there is no rubber clutch like the Yamaha 15, only shear pin which is OK. Thought it might be the bearing inside the prop slipping inside the prop, but not so. Maybe it's the drive shaft slipping inside the engine, however I am sure one would feel the splines clicking, which I don't! Any ideas would be greatly appreciated.

 

[mark.perkins]

Re: Yamaha 8 transmission slipping

alot of times the prop can be the wrong pitch or diameter for the size/weight of the boat/motor and how fast the boat can go. what happens is the prop actually loses its "bite" on the water. it feels alot like tires spinning on a car when hitting an ice patch. try calling a dealer and asking about pitching for your particular application. I hope that this can be of some help.

 

[Harry Usher]

Re: Yamaha 8 transmission slipping

Thanks for the tip - strange though why it has been running OK for almost 2 years with the same prop which has only minor indents from hitting rocks.