1979 70HP Merc Driveshaft Repair ?

[charliegiggles]

Hi,

I recently acquired a 1979 70HP mercury outboard. When I dismantled the foot to change the water pump I noticed a seal was missing from the top of the driveshaft and about 40% of the splines have been gouged away.

Should I just replace the missing seal and hope the driveshaft splines don't let go or should I attempt to have a machine shop fix it "if possible" or start looking for a used driveshaft as I imagine buying a new one will be very expensive?

Thanks.

 

[WillyBWright]

Re: 1979 70HP Merc Driveshaft Repair ?

I'm afraid that the problem is bigger than that. Worn driveshaft splines means worn crankshaft splines. If you put a new driveshaft into a worn crankshaft, it's going to wear faster than if you put that worn driveshaft back in. Considering the age of the motor, I'd just grease it up and put it back together. Then keep an eye out for a new motor. Besides replacing worn water pump impellers, now you know why it's really important to service the water pump fairly regularly to get some grease on those splines. When they run dry, they wear fast. Sorry for the bad news.

 

[charliegiggles]

Re: 1979 70HP Merc Driveshaft Repair ?

Well thanks for the advice. I guess you never know what you're buying when you buy used. Hopefully by greasing it up and putting the missing seal at the top of the driveshaft back in place it'll hold for a while. There was only one of the two seals on the top of the driveshaft so I bought the missing one.

I'll take pictures, grease it up well and see what it looks like at the end of next summer if hopefully it makes it that far.

Currently there is a moon shaped grove in all the splines with an apparent 40% wear in the center of the splines. This is dissapointing considering the motor has good compression on all cylinders and apparently runs well. I'm just concerned about taking off too fast and stripping the splines so I guess I'll have to take it easy in order to promote lifespan...