Alpha 1 gen 1 drive shaft o-ring

[BCreech]

I replaced my impeller in my alpha 1 gen 1. Only took off the lower unit. I looked up in the upper and there was a piece of an o-ring up there. In the Sierra impeller kit there is an o-ring the exact same size and a corresponding groove in the drive shaft on the lower. See pics. It looks like it goes right there but i have yet to find any videos or info saying it goes there. If I could get an answer I would greatly appreciate it. Thank you!

 

[Benny67]

Don't put it back. Mercruiser stopped putting that seal on the shaft in later production runs.

Check the seal in the upper housing. Chances are it's shot due to that seal getting caught in it.

 

[BCreech]

I did feel a seal in the upper. I lower unit goes in good without the o-ring on the shaft. I think your right. It's a 91 alpha 1 gen1. I have a manual ordered that will be here Tuesday. I'll check what it says.

 

[Benny67]

Dont forget to pressure test the drive before you put it back on the boat.

Even if you change the seal in the upper housing.

 

[BCreech]

Got the manual today. Looks like gen 1 has the o-ring

 

[harringtondav]

I'm guessing here, but Gen II Alpha's don't have an O ring groove on that shaft. Double back to back seals in the upper hsg. seal that shaft. I've been looking at this site's Alpha I parts pages, and can't make heads or tails from it. I'd say put it back together per the manual. If this includes the O ring, do it.

I've put seal kits in several Gen II Alphas, and I always end up with extras. I'm guessing the kits are for Gen I & II, and my spares belong in your drive.

 

[kip2001]

Many people on here say don't put that o-ring on the drive shaft anymore, it can cause more problems than it solves. I myself didn't see those comments until after I had closed up my lower unit and pressure tested it so I just left it be.

 

[harringtondav]

I'm perplexed by that O ring too, but I don't know the Alpha I upper gear hsg. sealing set up. O rings are never used to seal a rotating joint. So it must go into the upper pinion's bore, like the O ring that seals the engine coupler splines. But that is to keep the grease in the coupler. The spline joint shown is submerged in gear lube, so I don't understand it's need. I suspect it has to force it's way past the shaft seal lips which would really stretch them. So I understand the advice to forget the O ring.

Just a note. I use a Mityvac or similar vacuum tester to check mine. I tried to pressure test with a bicycle pump on a pressure gage once, and blew the Gen II seal carrier under the water pump up out of it's bore. I just checked YouTube and see 10# is the spec. Apparently I went way over that. If I can find one of the hand pressure testers shown, I'll start doing this.

 

[tricountytrail]

I tore up my seal when I last installed my lower to upper drives. I think I might have had the wrong oring(it was a little loose I had to force the drive up to fully seat)? What seals the drive shaft into the spline? There is a hole on the top of the spline the driveshaft goes into that would mean the cavity is full of oil that doesn't seem correct?

 

[tricountytrail]

Also which way does the seal install spring side up or down??

 

[Scott06]

Hey tri county best to start your own thread s posting on someone else’s , aka hijacking , this way no ones gets confused as to whose question they are answering .
as to the the original question the alpha one gen one - the oring was originally installed on top of the drive shaft , but merc found later that it tended to damage the upper oil seal when installing the lower unit into the upper so the recommendation was to leave it off. My personal experience I did it both ways and as long as you are careful not to damage the oil seal sticking the shaft in there you’ll be ok.

 

[tricountytrail]

Hey tri county best to start your own thread s posting on someone else’s , aka hijacking , this way no ones gets confused as to whose question they are answering .
as to the the original question the alpha one gen one - the oring was originally installed on top of the drive shaft , but merc found later that it tended to damage the upper oil seal when installing the lower unit into the upper so the recommendation was to leave it off. My personal experience I did it both ways and as long as you are careful not to damage the oil seal sticking the shaft in there you’ll be ok.

Also which way does the seal install spring side up or down??
Thanks but why I have you.

 

[Scott06]

Also which way does the seal install spring side up or down??
Thanks but why I have you.

Not sure what is so hard for you get ...Please start your own thread and ask your questions there. List your engine and stern drive serial numbers so people know what u are working on vs what the guys thread u are hijacking was working on as this one will most likely be closed by a forum Moderator soon enough I'm sure...