Drive shaft replacement 1991 evinrude 70 hp ( threads gone)

[WT2]

I have replaced the driveshaft twice and I am starting to wonder if the problem might be in the crank. When I bought the boat the bolts that held the lower unit to the motor were stripped and very loose. I found this out after a half of season of running it. After I fixed that issue I failed to lube the threads or put a new seal in. This time I shimmed the drive shaft and have some real thick synthetic lube but I hate to ruin another shaft. Is it reasonable to think that I may have ruined the splines in the crank? Each time the drive shaft went out I was pretty surprised that it did because of the situation. They usually last about two years of moderate use. Any thoughts will be appreciated.

 

[racerone]

Are the splines at the top the problem ?-----Or are the threads for the nut on the bottom the problem ?----Pictures ?-------And yes if the splines on top are not greased you will have problems.

 

[Chinewalker]

If you've torn out the splines from the driveshaft, it is usually an issue compounded by not servicing the o-ring and grease of the splines when water pump is serviced. The crankshaft is steel and will rust. It starts to go, then once they're partially gone, they take the driveshaft splines out as they're typically softer stainless. It may work for awhile with a new driveshaft, but if the crank splines are indeed worn, they'll eventually take the splines off the new driveshaft, too...

 

[WT2]

I put the drive shaft into the crank last night and when it was too far up it had minimal play. When I pulled it back a little it seem to have too much play. I dont want to buy a new crank and too worried about buying a used one. Has anyone had any luck with shim stock and real thick grease. I know it is a bandaid approach but I know the motor will cost more than it is worth.