Mercruiser Sterdrive Lower unit driveshaft no splines??

[Recelect]

1983 Mercedes boat, 120 horse mercruiser with Alpha 1 Sterndrive.

So I purchased this boat with the sterndrive already torn apart. The old owner said it needed a new prop shaft (the old one was twisted) so I bought a new shaft and started dissasembling the lower unit. When I went to take the drive shaft out, I realized that it did not have splines on top (which made it hard to release the nut on the bottom of the drive shaft) is this some sort of weird setup with this unit? or did the splines break off when they damaged the prop shaft?

The top of the drive shaft is clean and "looks" normal. I would think if there were splines, and they were twisted off, the drive shaft would look pretty narly. I have attached pictures so you all know what I am talking about....


Please help this rookie!

 

[Bt Doctur]

Re: Mercruiser Sterdrive Lower unit driveshaft no splines??

drive shaft is sheared , the missing splines shoud be found in the upper section.looking at the prop shaft my guess it took a very severe strike. you can expect damage in the upper housing now or shortly thereafter you put in in service.may even find some broken teeth in there now.

 

[Bondo]

Re: Mercruiser Sterdrive Lower unit driveshaft no splines??

Ayuh,.....

That's pretty Typical,... It Snapped Off at the O-ring Groove.....

Mercruiser did away with that o-ring,+ it's groove in later models....

 

[HT32BSX115]

Re: Mercruiser Sterdrive Lower unit driveshaft no splines??

That's amazing!

I have never seen a lower so thoroughly destroyed! (although I'll bet the guys who do this for a living see this all the time!!)

You need a LOT more than a propshaft. In the aviation world that would be called a "Sudden Stoppage" It usually causes all sorts of other damage.

You can probably plan on rebuilding the upper too. really severe damage is usually not restricted to one part. The whole drive shares the oil so any metal pieces that are loose in the (lower) oil are probably in the upper too.

Have you considered just replacing the whole thing?


Your best bet? go buy a complete Sterndrive Engr drive and replace the whole thing.

Oh....you need to pull the engine and replace the coupler too!

 

[Recelect]

Re: Mercruiser Sterdrive Lower unit driveshaft no splines??

I should add, I cut the prop shaft so My puller would reach the bearing carrier to pull it out. i figured since i was replacing it anyway and since I did not want to buy another puller, I would cut it so the one I had would work...

 

[Bondo]

Re: Mercruiser Sterdrive Lower unit driveshaft no splines??

Ayuh,.....

For the replacement Costs for those 2 shafts,.......
You're probably already up to the price of a replacement SEI Drive,..... Complete....

 

[Haut Medoc]

Re: Mercruiser Sterdrive Lower unit driveshaft no splines??

Spare yourself the agony & spend the $1200 for a new after market drive from SEI.......​

 

[wca_tim]

Re: Mercruiser Sterdrive Lower unit driveshaft no splines??

this sounds familiar... Looking for something like this??? (pic below)

had the same thing happen... remaining portion of the shaft came out of the upper easily with a little gentle tapping. After doing the homework, I went with an SEI lower only. Looked at the internals on my then current upper and it was in really good shape. The lower came with water pump / impeller installed, has a beefier drive shaft (no o-ring groove, etc...) and was absolutely no trouble to install. It did make a little bit of extra noise for a while (gears not lapped at the factory), but broke it in much like recommended and in the vein of my typical overkill, I changed the gear lube every 5 or 10 hours until there were no more metal filings / powder in the lube. Similar to the stories of others, I've been very pleased with the experience with SEI. Consider that if you have the shaft replaced by someone competent, you're looking at as much more cost (IF no other work needs done in there when get it apart), probably no warranty, and will still have 20+ years of wear on the rest of the lower. No brainer in my book... go with new lower minimum, the whole drive if you can affort it...