Upper drive seal

[Kirk Gibson]

Yes it appears that way

I agree,
Looking at the diagram it does appear like it can be done without removing the bearing cup.
As soon as I get a retainer wrench I will have a go at it and we will see.
Thanks
Kirk

[admin]

We do indeed use a single seal that is double lipped. That is the standard for the OEM also.

When you pressure tested the upper, did you make sure to hold down the socket? Otherwise the pressure will just pop the socket up and allow it to leak. I am also not sure if the socket would work properly. You could put both halves together and just pressure test the complete drive. That will tell you for sure.

That seal can definately be replaced without pulling the race.

Tech Support

[Kirk Gibson]

Thanks for the reply

Yes I held the socket in place (it did indeed want to pop out) and it leaked real good around the socket.

I could put the halves together without oil and check it that way and if it holds then I guess I'm ok ... but that oil had to go somewhere and that must mean a leak somewhere ... right?
The lower unit pressure tested great.

If I do have to replace the seal ... it seems as there is room for a second double lipped seal above the one that is there now ... would it hurt to put in 2 double lipped seals ... just for security?
Thanks for any suggestions.

Kirk

[admin]

Yes, the oil had to go somewhere, I am just not sure it came out that spot. I rarely see a drive leak there. Best to put the halves together and test it. I have never looked to see if there is room for two seals. I can't think of a reason not to put two there if it will fit, but I have never tested it.

Tech Support

[Kirk Gibson]

I may have found the leak

OK,
I finally was able to get to the reassembly and pressure testing of the entire unit today.
After it was back together I pumped (with a bicycle pump) 15 psi ... lost 1 psi removing the pump so it was at 14 psi.
I let it sit for 1 hour and then it was at about 13 psi.
I sprayed soapy water around the upper drive shaft seal and no bubbles.
I then moved the shift shaft and heard hissing!! A-ha! You were right ...it doesn't appear to be comming from the upper gearcase seal!
I sprayed soapy water around the shift shaft seal and big time bubbles!
But if I turn it back the hissing and bubbles stop. So it only leaks in one position ...

So it looks like I need to replace that. But there never was signs of oil comming out of that hole when I disassembled everything and there were no signs of oil in the water when we were stopped. Also I wonder (if this IS the place where oil was lost) why I could smell gear oil only when I opened the engine hatch? I traced the line from the reservoiur to the transom and no leaks.
This is strange because the drive has performed great ever since I bought it from SEI ... this is the first problem.
Is the shift shaft seal pretty straight forward or do I have to take apart the entire lower unit?
Thanks for any help.
Kirk

P.S. How much pressure (psi-wise) normally builds up in the drive during normal usage? Is 15 psi enough?

[admin]

15 PSI is enough pressure, the drive shouldn't get an higher than that under use, unless it is overfilled, but you have the reservoir bottle anyway, so it realy shouldn't build up much pressure. I am not sure why you were smelling gear lube. Did you have any gearlube in the u-joint bellows?

I would recommend just changing the complete shift bushing assy. Merc # 815921A13
When changing it, you will need to remove the shift shaft in the lower. Make sure and do this with the drive in an upright position, you do not want the shift crank in the lower to move out of alignment when the shaft is out.

Tech Support

[Kirk Gibson]

Thanks for all your help.

Thanks for all your help (even though mine is out of warranty)
I carefully pulled the shift shaft assembly and they are holding the new part for me at the marina. I will pick it up tommorrow and verrryy carefully reassemble it. Then go for the pressure test again.
There was play in the shaft at the seal.
There was no oil in the bellows BTW.
The smell part is still a mystery.
Thanks, I will let everybody know how it goes.
Kirk

[Kirk Gibson]

Quick question(s)

OK,
Just replaced the entire assembly and it went back together real smooth.
The only part that didn't come in the kit was the rubber "sleeve" just below the 90 degree bend in the shift shaft. The old one was split. The SEI part # in your diagrams is 98-116-24.
When I went to buy one the Merc diagrams at 3 different marinas all showed a different part which it called a "washer" but it is rubber and seems to fit right over the oil seal so I guess that is a Mercruiser update for the sleeve or something. Is that correct?
BTW - What is the purpose of that sleeve? The service manuals don't say anything about sealing it with anything ... just to push it down until it contacts the oil seal ... so how can it keep water from the seal?

I am going back out to put it back together and pressure test it again.

Thanks for all the advice.
Kirk

[admin]

I think it is to keep junk away from the seal, or at least add a little more protection in that area.

Tech Support

[Kirk Gibson]

Pressure test result

After 18 hours it went from 15 psi to 14.5 psi ... I moved the driveshaft several times, moved the shift shaft several times, sprayed soapy water all over (no bubbles) and it seems to be holding OK.
I might add that when I pressurized it the temp. outside was about 96 degrees and this morning when I checked it out it is about 80 degrees and it sat all night to cool off so that may account for the .5 psi.
I will let it sit and see if it comes back up ...the temp. today is supposed to get near 100.
I think this thing is sealed, I will give it another day and then put it back on the boat.
Thanks again for all the good advice.
Kirk

[Kirk Gibson]

Hello again

Hello again,

I got my engine all back together and drive installed and was setting the timing etc. when the engine temp alarm went off!
The outside temp. here yesterday was around 95 with high humidity and that must have got to me as I forgot to put the muffs back on (after warming the engine up I took them off to take a break before setting the timing) and I immediately shut it down.
Knowing I had probably fried the impeller I pulled the drive (I'm getting pretty quick at that ..LOL) and found after running about a good 5 minutes dry that the impeller looked like brand new (which it is) and looks like nothing ever happened. This was puzzleing as I have always heard if you run it dry for even a minute that you will destroy your impeller.
I replaced it with another new one I had just to be safe.

When I pulled the drive I noticed 1 drop of lube oil sitting on the gimbal bearing. Just 1 drop.
Now the engine had about a total of 30 minutes run time with the drive on and the reservoir didn't drop a bit so I am thinking my replacing of the shift shaft assembly (earlier in this post) corrected the original leak. And I pressure tested it to be good before re-installing it. I now have the pressure test rig on it again and have been turning the shaft over and over and pressure seems to be holding like a rock at 18psi after a couple hours.

I still feel it is ok but why the evidence of oil? Should that small amount concern me?
Also would it make a difference if I pressure tested the drive with oil in it?
Would it damage anything to test it that way?

Thanks for all your great help.

Kirk

[Kirk Gibson]

Almost forgot

Oh another thing I almost forgot to ask, (along with my previous thread today)

I never found any water in the drive oil ... is there any need to perform a vacuum test on the drive.

I can't find anywhere in any Mercruiser stuff that calls for a vacuum test...however I read all over the forums where people test both ways...is this necessary?

Thanks again

[admin]

Sorry for the late reply, I was working out of the office today.

Concerning the drop of lube by the gimbal bearing, I wouldn't worry about it. Just make sure to turn the drive while you are pressure testing it so that seal gets some movement. Always turn it by the input shaft and always clockwise, the way the engine would turn it.

If the impeller was brand new, maybe it was installed with some grease that kept it from melting. 5 minutes is along time, so I am surprised there was no damage also. Was there evidence of a black powder? I would imagine if just the tips get hot, it might just turn the outer edge to powder, and then after running it longer it completely destroys itself.

Concerning a vacuum test, It is not recommended, probably because it doesn't hold much vacuum since there are seals that are only keeping stuff in, such as the upper yoke seal. Since water should never be in that area, they only use a single lip seal. If you were to vacuum test it, it will only hold about 5-7 psi.

Tech Support

[Kirk Gibson]

Thanks once again

I must have just got lucky as far as the impeller ...there was no black powder or any signs of it being damaged.
Would it hurt anything to pressure test it off the boat with oil in it?
If not should I still pump it up to 15 psi?

Also while testing it (oil in or dry) how many times would you reccomend I turn the drive shaft ...I turned it a good 20 times or so...is that enough?
Thanks
Kirk

[admin]

You can pressure test with oil in it, but air is thinner than oil, so it might not show the leak with oil in it. I wouldn't check it with oil. 15 psi is the max. You really only need to pressure test it for 10 or 15 minutes and then push, pull and turn all the shafts a few times.

Tech Support