Lower gearbox oil leak - Merc 'R'

Cresco750

Petty Officer 2nd Class
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Jul 7, 2012
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192
Hi
Having just got my new-to-me boat up and running after being inactive for over twelve years I have discovered an oil leak from what appears to be from around the prop shaft leading from the lower gear case (Mercruiser R leg). Since getting the boat going a couple of weeks ago I have only managed to put about an hour of water time on it, and then stored in a relatively cool shed. No leaks were evident in that time.
In the last couple of days it has been sitting at its new home in an open air dry stack which has been exposed to some nice warm, sunny days, and this morning I arrived to find a fairly significant puddle (estimate about a quarter of a cup?) of nice new blue gear oil under the leg!
My question is; is it possible that due to expansion in the heat the gear oil has simply become 'over full' in the gear case and been forced out under pressure past the prop shaft seals, or is it more likely simply as a result of faulty seals which I will now need to replace?

Thanks n advance.
 

Bondo

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70,465
Re: Lower gearbox oil leak - Merc 'R'

or is it more likely simply as a result of faulty seals which I will now need to replace?

Ayuh,.... More than likely....
 

Cresco750

Petty Officer 2nd Class
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Jul 7, 2012
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Re: Lower gearbox oil leak - Merc 'R'

Or.....could it possibly be leaking out the top seal? I did just put a new water pump in, along with new seals on the housing but I guess its possible that one if those seals may have got a nick in the lip during installation?
 

Cresco750

Petty Officer 2nd Class
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Re: Lower gearbox oil leak - Merc 'R'

Ok, I've just spoken to a local Mercruiser service agent and he's telling me that they would normally pull the whole out-drive assembly off to source and fix a leak like this! Does this sound right? I can just see the $$$$$ mounting up!
I would have thought that it could be done with the leg still attached to the boat, or at most drop the lower gear box off?
Is this normally regarded as a straight forward owner -serviceable issue, or do many run into problems with removing the carrier and retaining ring from the gearbox? Can the seals be removed and replaced without having to remove the carrier at all?
 

ktbarrentine

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Dec 12, 2011
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Re: Lower gearbox oil leak - Merc 'R'

Ok, I've just spoken to a local Mercruiser service agent and he's telling me that they would normally pull the whole out-drive assembly off to source and fix a leak like this! Does this sound right? I can just see the $$$$$ mounting up!
I would have thought that it could be done with the leg still attached to the boat, or at most drop the lower gear box off?
Is this normally regarded as a straight forward owner -serviceable issue, or do many run into problems with removing the carrier and retaining ring from the gearbox? Can the seals be removed and replaced without having to remove the carrier at all?

What the mercruiser mech will do is what you can do yourself with moderate skills, basic tools and a fabricated test set-up which you can learn about on this forum. They will drain the oil, remove the drive from the bell housing, then do a 15 PSIG pressure test (with compressed air) and a soap-bubble spray-on test to locate the (hopefully) one faulty seal you have.

You can do this yourself on a Saturday and could even be back on the water by Sunday (provided you can get the part you need quickly).

best of luck and there are plenty on here that can guide you in the work, plus you can get the right service manual/instructions here and also lost of links to how-to videos for your drive.

if it does turn out to be prop shaft seals, then of course there is abit more to do, with special tools. But...if you isolate the leak to a specific area, you are in a better position to be able to work with the shop and save some money.

And then again, you may even start considering the purchase of an SEI replacement drive and put all your worries to bed.:D
 

thumpar

Admiral
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Jun 21, 2007
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6,138
Re: Lower gearbox oil leak - Merc 'R'

Pulling the drive is not hard. It is 6 nuts on the drive and 2 nuts on the rams. Then just pull it off. That is a normal maintenance thing to do to change the impeller, check bellows/gimble bearing and do alignment.
 

Cresco750

Petty Officer 2nd Class
Joined
Jul 7, 2012
Messages
192
Re: Lower gearbox oil leak - Merc 'R'

And then again, you may even start considering the purchase of an SEI replacement drive and put all your worries to bed.:D

Well I would, but unfortunately the cost of shipping and taxes to where I live makes fixing the old one still the most affordable option.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Lower gearbox oil leak - Merc 'R'

It's easier to drain and test the drive as a whole unit. Yes, you could pull the lower unit off and test just that, but if the leak is the bottom seals in the top box (the oil still appears at the same place as a prop shaft seal) then you have to go back and get the top box off the bell-housing.

If the leaking seal IS the prop-shaft seal, then it is possible to replace them (there are 2 seals on the prop-shaft) without removing anything else, but it's not easy. I prefer to just pull the bearing carrier and work with that on it's own.

Here's a link to the service manual. Have a read through and see how you feel about it. If you decide to tackle the job yourself, then we are all here to help you...

https://docs.google.com/open?id=0B1TAvwZ3TjhfOVRUNEk0anBUR3lQYTkwcUh5RElUQQ

The first thing you need to do is get the drive off, drained and pressure tested. It may look like a prop-shaft seal(s), but until the pressure test you don't know.

Here's a video to help you take the drive off. -> http://youtu.be/w3O63YTOhn8

Chris............
 
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