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Author Topic:   Lower Unit Seal Leak Suspected
Dr T posted 07-29-2002 11:18 AM ET (US)   Profile for Dr T   Send Email to Dr T  
Last year, I winterized my 1982 Johnson 35-HP outboard engine and boat in Broomfield, Colorado, elevation 5,500-feet ASL. In early July, I took the boat up to Steamboat Springs, elevation about 8,000-feet ASL for its annual dose of mountain climbing. I got the lower unit pretty full of lube when I winterized it.

I used the boat a couple of weeks ago, and it has been sitting on the trailer. Yesterday, as I was getting ready to come back down from the mountains, I noticed a yellowish sheen to lower unit from about the hub down and oil spots on the ground below the hub. I noticed this in passing and did not have the opportunity to inspect it closely. Am I about to lose an oil seal on the lower unit? Or is this leakage normal on 20-year-old outboard? Thanks--Terry

Bigshot posted 07-29-2002 11:55 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
yup!--Have it pressure tested and repair what is leaking. Good thing is you caught it in time and it was leaking out, not in. Not too bad, can probably do yourself but I would'nt.
Dr T posted 07-29-2002 01:51 PM ET (US)     Profile for Dr T  Send Email to Dr T     
Thanks, Nick. I will be bringing it out of the mountains next weekend. It may see a little light use (~1 hour or so) before then.
Bigshot posted 07-29-2002 02:03 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I would'nt. You have good lube now, 1 hour bath might change that and turn a $100 repair into a new lower.
whalerron posted 07-29-2002 11:47 PM ET (US)     Profile for whalerron  Send Email to whalerron     
bigshot is right. If that unit is seeping oil, it could possible leak in both directions. When you run the motor in gear, the lower unit starts generating heat. When you shut it down, that lower unit will start to cool and as it does, it could suck seawater into the gearcase. It doesn't take much water to displace lubricate from the bearings and gears. Once that happens, if it hasn't already, get your wallet ready.
Dr T posted 07-30-2002 07:50 AM ET (US)     Profile for Dr T  Send Email to Dr T     
Understand. But that would finally give me an excuse to re-engine the boat. :-)

With the water temp in the mid-50s and fresh water, I don't think it will get very hot.

I will do a close inspection on Saturday morning to see what I have.

Tom W Clark posted 07-30-2002 10:25 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

You'll be fine. A slight leak of oil is not indicative of a complete gearcase failure. You may well get a little water in the gearcase after running it for an hour or so but it's not going to kill the gearcase. Maybe it would if you run it all summer like this. You might want to top it off before going out to confirm that there is enough oil in there however.

Drain the oil when you get back down and you'll see it looking "cloudy" or "milky" from water mixed with the lube. It is not a big deal to reseal the gearcase.

Dr T posted 07-30-2002 01:30 PM ET (US)     Profile for Dr T  Send Email to Dr T     
Thanks, Tom. I will just need to pick up some gear lube before I go up to the mountains.

The way the kids look forward to the boat up there, it is awfully hard to say "No", even at the expense of potential mechanical failure. I will be stepping the prop down to an 11x13 to cut down on the stress to the drive train (10.5 x 11 is just too much prop at 8000 ft--even though it works fine at 5000 ft).



Salmon Tub posted 07-30-2002 02:46 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
Tom hit the nail on the head, if you want to be even more safe, do this: Drain fluid now into an empty jar and save. Remove prop and clean all signs of oil from shaft, seal area and housing. Fill with new oil and run inside a big garbage can with water for about 1/2 hour in gear. Listen for any difference in sound coming from the lower unit. 1/2 hour should be ok since you would be doing this at low speed. Remove promptly and keep in lowered position. After oil settles (overnight) remove oil into a jar and compare to first. If you trim the engine up out of the water when not in use, you will keep the water from seeping in, and keep the oil from seeping out. Also look at the water in the garbage can for signs of oil, and around the lower unit for oil during the following days after the test. I have an old Monte Ward 6hp that used to drink water all the time. Changed oil every second use.
Keep in mind, this is not a fix, but just a salvage for an upcoming trip or weekend. A little extra oil is cheaper than a lower unit and the test should give you an idea of how much water if any is coming in. Most problems with water in the gearcase come from the water sitting in there and freezing or from sitting there too long and causing corrosion.
Bigshot posted 07-30-2002 02:46 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Just be careful T!

You sure it was not exhaust spooge dripping out? Usually if it is leaking, seal is pretty bad but milky lube should be coming out.

Dr T posted 07-30-2002 04:14 PM ET (US)     Profile for Dr T  Send Email to Dr T     
Thanks for the advice. I will have a much better idea on Saturday morning.


Dr T posted 07-30-2002 04:18 PM ET (US)     Profile for Dr T  Send Email to Dr T     
The comments have given rise to the following thought:

By Saturday, the motor will have been sitting on a trailer with the motor down and unused for about 3 weeks. Maybe I should drain out a bit of the oil into a clear container and top it up with fresh lube. Then I could let the stuff drained out sit for a while to determine if any water is present.

This is basically what you do when testing the fuel on a light plane during preflight, and should give me an idea of what condition the lower unit is in.

Thanks again.


Salmon Tub posted 07-30-2002 04:41 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
If you drain and then have to let it sit to see if water will seperate, then it is not as bad as you think. I had a shot glass of water, then milk, then the remainder of the oil pour out when I first discovered the problem.
Dr T posted 07-30-2002 07:03 PM ET (US)     Profile for Dr T  Send Email to Dr T     
Good to know what to look for. Thanks.

With any luck, Nick will be right about the exhaust spume. I've only run the boat once this season, and I was quite liberal with the fogging oil when I put it up last year.

An off-the-subject observation is that many of the mountain lakes in Colorado that I have looked at are ~20-30 ft down over this time last year because of the snow drought last winter. The exception thus far seems to be Stagecoach, which is south of Steamboat Springs. I think that it is being held in reserver since very little water is flowing down the Yampa this summer.

simonmeridew posted 07-30-2002 08:07 PM ET (US)     Profile for simonmeridew  Send Email to simonmeridew     
Dr T
When you serviced the lower unit last Fall did you check to make sure both the large headed screws had gaskets on them when you screwed them back into the lower unit? If not that is where they are leaking.
BTW you remove both upper and lower screws to drain, and fill from the lower hole--not the upper--until it starts coming out the upper hole. This assures a full gearcase.
flyguy posted 08-01-2002 09:05 AM ET (US)     Profile for flyguy  Send Email to flyguy     
i thought the boat was cheap when i bought it...the waterpump seals in my outboard were shot and was actually creating pressure in the lower unit. water was getting in, gear oil was being pushed out, it was a mess. because i would change the oil every time i got home the mechanic said everything inside was in very good condition. sure it was a few $$ in quicksilver high performance gear lube but in the end i saved a lot of $$. we changed the entire water pump and the rear prop seal. you can take it out if you change the gear lube but obviously the sooner you get it fixed the better.
Dr T posted 08-04-2002 10:02 AM ET (US)     Profile for Dr T  Send Email to Dr T     
I examined the lower unit yesterday. The lube appears to be leaking from the seal around the prop shaft. I would estimated that about 1 to 2 fl. oz. have leaked out so far, judging from the size of the greasy spot (about 2 or 3 in. in diameter).

Just how big a deal is it to change out this seal?



kingfish posted 08-05-2002 10:44 AM ET (US)     Profile for kingfish  Send Email to kingfish     

FWIW - incredibly small amounts of oil can make incredibly large oil stains - if your greasy spot is only 2"-3" in diameter, I have to think you lost *far* less than 1 to 2 fl. oz. Maybe a tenth of that-


Dr T posted 08-05-2002 10:52 AM ET (US)     Profile for Dr T  Send Email to Dr T     
So I discovered yesterday. I drained a bit of the lube, and other than some sludge at the bottom (a little cloudy and some dark streaks), it was nice and clear. When I pulled the prop to inspect, I found that the prop washer was a bit loose.

So, I guess I was just being paranoid. But it would be nice to have a new motor....

Thank you all for your help.


jstachowiak posted 08-05-2002 11:42 AM ET (US)     Profile for jstachowiak  Send Email to jstachowiak     
I just had the same problem. I just had my '79 90HP Mercury in for a new water pump impeller and he changed the gear lube for me too. I discovered oil on the prop and took the prop off and found oil sitting in the housing, turned out to be residue from the change the shop did and not a leak.
les i posted 06-13-2012 03:22 PM ET (US)     Profile for les i  Send Email to les i     
[Revived this discussion after it had been dormant for ten years. Please start a new discussion in REPAIRS/MODS for your new topic. Thank you--jimh]

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