Johnson 70 broken drive shaft question

[markl]

I have a 1982 Johnson 70. I dropped the lower unit to replace the pump impeller this fall. While doing this I uncovered a failure waiting to happen. The drive shaft broke off just below the crankshaft spline leaving the spline end in the bottom of the crankshaft. I know this was a failure that had been in the making for several years because the fracture surface on the shaft was quite corroded. Plus, removal of the lower unit was pretty easy. What luck! :-0<br /><br />My question, what should i do with this? Is it worth fixing? The motor ran strong with good compression last season. How much of a job is replacing the shaft? I can take the power head off this winter and remove the splined end from the crank, but am not experienced at lower unit work. What is my best option? Any info appreciated.<br /><br />Mark

 

[BillP]

Re: Johnson 70 broken drive shaft question

I'd replace the shaft and not worry about it. 70hp OMCs are some of the best. If you find a used drive shaft pay close attention to the area where the seals ride, especially at the water pump. If those surfaces aren't smooth they will eat seals. <br /><br />OMC had a bad batch of drive shafts years back but I don't know if it included 1982 motors. I think it was mid to late 80s. Anyway, they found the supplier didn't make the shafts to OMC specs...the result was many broken shafts from guys who wave jumped. Maybe one of the OMC experts know the years.<br /><br />Bill P.

 

[R.Johnson]

Re: Johnson 70 broken drive shaft question

Did you hit an obstruction with this engine? If you did, you have a bent exhaust houshing. This will break the drive shaft at the top of the spline. I'm not aware of drive shaft fialures on these engines for any other cause. If you replace the shaft, and not measure the housing, it will break again.

 

[markl]

Re: Johnson 70 broken drive shaft question

I just bought this engine last summer, so I dont know its history. It does not appear to have hit anything hard. The original owner said it was a great engine, and I believe him.