Worn Spline Repair

[Mumbles]

I’ve ‘repaired’ worn driveshaft splines before by welding a socket onto the crankshaft and then cutting a hex on top of the driveshaft to fit the socket and also by making one shaft out of two by cutting the good lower splines off one shaft and then welding them to the top of the other shaft and I’ve also seen the splines joined by using epoxy but I think this repair takes the cake.

Today’s garage sale find was a salty 1976 Evinrude four horse for five bucks which I got running after doing a bit of magneto work. Since it didn’t run too bad, I thought I’d service the water pump while the carb was soaking. Once the gearcase was off, I noticed there was a chunk of the drive shaft missing in the upper spline area. Looking up the exhaust housing with a flashlight, I could see the missing piece in the end of the crankshaft. That’s weird I thought. I’ve never seen that before. Anyway, after getting the powerhead off, I tried to get the piece out of the crank but it wouldn’t budge. After cleaning it up a bit, I could see it was welded to the crank. Once the weld was ground off, the piece came out and it all started to make sense.

The splines left on the shaft are worn and I could hardly even see any in the crank so this thing must have been slipping quite badly. The piece which was welded in the crank isn’t the missing chunk out of the driveshaft but what looks like a bolt which has been cut down. It has threads on it. What I figure happened is, since the splines were shot, someone cut or ground away part of the driveshaft and welded a corresponding piece into the crankshaft to act as a drive key. It worked and I’m still smiling thinking about their ingenuity! They must have watched every episode of MacGyver back in the day!

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[billw]

It saves an otherwise dead motor. I like it! It will be interesting to see if any vibration can be noticed from it.

Edit: Oh, I get it, you took the piece out of the crank. So you’re not going to be running it that way?

Long live American manufacturing!

[pm-t2]

Wouldn’t be too hard to save the original driveshaft if you spliced a new piece on the end and cut the splines in a mill.

Since Bill Andrulitis taught me how to properly cut splines without specialized tooling, I’ve done it several times… a few of them even fit, actually

Best,
PM T2

[20mercman]

quote PM T2:

Wouldn’t be too hard to save the original driveshaft if you spliced a new piece on the end and cut the splines in a mill.

Since Bill Andrulitis taught me how to properly cut splines without specialized tooling, I’ve done it several times… a few of them even fit, actually

Best,
PM T2

I wish I knew how to do that, it would be a great skill to have. I have extended drive shafts by cutting, center drill, add a length of drill rod and fill with weld. Turn on a lathe and they work great. The shaft needs to be the same diameter to get the pump on, so I like the weld repair method. As for this repair that Mumbles has, this is kind of neat. I have an old TN that Kevin was assembling from parts that the splines in the crank are wiped out. Not a bad idea for something that is really scrap otherwise.

Steve

[PugetSoundBoater]

That was a creative repair that was done. Yours will be better Mumbles.
As for the reason the splines wear,I have read it can be from the midsection being bent. The result of the now misaligned driveshaft top splines creates the wear. In addition to that scenario, salt water damage ,a missing o ring below the splines or lack of grease on the splines could wear the splines.

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[reivertom]

That is a fine bit of BBE (Backyard Bubba Engineering). :^)

[RICHARD A. WHITE]

I have made standard length stainless steel Big Four drive shafts… fun times…

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[fleetwin]

I’m usually pretty skeptical, but I’m not afraid to admit that that repair looks pretty good to me, why do anything with it at all? The condition of the rest of the engine surely does not warrant any big heroic engineering repairs. Replace the impeller, pack the driveshaft heavily with thick grease and put it right back together!
Let me know if I am missing something here….

[Author]

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