'75 135hp worn driveshaft splines on top

[pcrussell50]

bought this boat last fall, and it runs like a top.

still, i decided to drop the lower unit and change the oil and the water pump as a preventative measure...turned out to be a waste, because the impeller and oil were in great shape. oh well, now i have peace of mind.

that was all fine, except that i noticed the splines at the top of the driveshaft are worn. they are no longer dull and flat on their tops, they are now sharp. it doesn't appear to be from any singular incident, just plain old age, as far as i can tell. there's no galling or anything.

now the part i need opinions about. i can get a new shaft for like $550...and I might just pony up for that...but...i don't want to do that if there is a high likelihood that the crankshaft's internal splines are equally worn.

i'm clinging to hope that the crankshaft spline material is harder than the old '75-era stainless driveshaft's splines, and is thus probably not worn too badly.

what do you guys think? likely that the crankshaft's splines are ok? if there is high likelihood that the crank's splines are good, i might just pony up for a new shaft.

it would break my heart and make me sick to throw away this otherwise great running motor...damn.

-peter

 

[Dhadley]

Re: '75 135hp worn driveshaft splines on top

Take a flashlight and look up into the midsection. What do the crank splines look like?

 

[crb478]

Re: '75 135hp worn driveshaft splines on top

You will probably have to pull the powerhead to get a good look, but that is the only way I know for you to see it and measure any wear. Before I spent 550 for new I would run it and look for a used one.

 

[pcrussell50]

Re: '75 135hp worn driveshaft splines on top

You will probably have to pull the powerhead to get a good look, but that is the only way I know for you to see it and measure any wear. Before I spent 550 for new I would run it and look for a used one.

thanks for that. i figured pulling the powerhead was going to be the "right" way to inspect. i was just holding out hope that the old hands would jump up and say, "sure, happens all the time. the driveshaft splines always wear faster than the crankshaft splines. just go get a new shaft and you'll be good to go" er, or something.

-peter

 

[tx1961whaler]

Re: '75 135hp worn driveshaft splines on top

I'd say "please post a picture"
You may be worried about nothing.

 

[Dhadley]

Re: '75 135hp worn driveshaft splines on top

It happens. No need to pull the powerhead although that's easy, just look up to the bottom of the powerhead and see what the splines look like. Not a big deal.

 

[pcrussell50]

Re: '75 135hp worn driveshaft splines on top

It happens. No need to pull the powerhead although that's easy, just look up to the bottom of the powerhead and see what the splines look like. Not a big deal.

i did that, and near as i can tell, the splines inside the crankshaft _look_ good. but they are 20 inches away, so i'm not sure if i can really ascertain their health for sure.

say, how do they get splines inside the crankshaft, anyway. is it an insert? if so, is it replaceable?

-peter

 

[crb478]

Re: '75 135hp worn driveshaft splines on top

If they look good and you are comfortable that they are not obviously worn then see if you can get your hands on a good driveshaft and slide it up into the powerhead. Once it seats twist it back and forth to see if it is loose or if it fits in there tight. If it doesn't feel sloppy put the new driveshaft in the lower unit and run it.

 

[pcrussell50]

Re: '75 135hp worn driveshaft splines on top

If they look good and you are comfortable that they are not obviously worn then see if you can get your hands on a good driveshaft and slide it up into the powerhead. Once it seats twist it back and forth to see if it is loose or if it fits in there tight. If it doesn't feel sloppy put the new driveshaft in the lower unit and run it.

quick update...

i did that very thing. i bought a new driveshaft, and finally brought it out to where i keep the boat, in needles, ca near lake havasu. [i live several hours from there, by the ocean, this boat is a freshwater boat], so this weekend was my first opportunity to get back since i started this thread.

in any event, i pulled the lower unit with the worn out drive shaft, and slipped in the new shaft and twisted it. there was very little torsional play, even though it slid in and out easily with a little lube.

i consider this good news, and will proceed with installing the new driveshaft, unless one of you all can convince me why i shouldn't.

thanks for all the ideas up to this point.

-peter