Yamaha 70hp runs well and drives boat well at low revs, when increasing revs no extra drive occurs from propeller, engine revs well and it appears a clutch may be slipping, do these engine have a clutch, is this a common problem

graeme clark, September 2007

check that it has a shere pin which goes through the prop and the shaft it roatats on.the pin is there so if you hi the bottom or get rubbish on the blade the pin will break insted of dammaging the gearbox.get the propper pin as usualy they are made from iron so they snap and can take a lot of power without failing.dont be tempted to put a bolt in its place!!

brock, November 2007

the prop needs changed has been hit hard the rubber in the middle acts as a clutch to save damage to engine rubber slips only thing to do is to replace the prop hope this helps

rickie, October 2007

The hub on the prop is prob. "spun". Take the prop off and look between the inner splined brass hub, and the outer prop housing. You should see a rubber bushing between the two. The rubber is a coushion but will start to slip over time or due to abuse.The damage should be obvious (rubber shreds or globs comming out). If not, mark the inner hub and the outer prop housing, run the motor in gear, fast enough so that you notice the slipping. Then look at the marks and see if they are still lined up. The inner hub should not move at all, compared to the rest of the prop.

BA, October 2007