Gear Oil Leak

Waz · 08 July 2010, 10:56

Hi folks

Wonder if anyone can advise? Drained & replaced the gear oil on my 1990 Mercury 40hp 2-Stroke last night using a Quicksilver bottle pump & lube. Followed the advise on link http://www.nitroowners.com/projects/...nitproject.htm to compress any trapped air althought noted resistance to adding a "Couple more pumps with the vent screw in". As the man suggested, "If any trapped air exists, you'll hear a *puff* of air come out around the edge of the vent screw" so thought all was ok.

Problem is I noticed a dribble of lube coming from holes above the vent screw, wiped away a couple of times & took the attached picture when the leak had slowed. Just to say with the vent screw removed again only a small amount of lube came out past the threads so I had not overfilled.

My worry is, what are these holes in the skeg for & why would oil be leaking out? Could I have blown some sort of gasket trying to pump with the vent screw in? If oil can come out my guess is salt water could get in?!

Hope you can help,

Thankyou

Nos4r2 · 08 July 2010, 12:59

I think your driveshaft seal or shift shaft seal may have given up.Oil shouldn't be coming from there.

Drop the lower unit and investigate where the oil is coming from. Don't put it in the water 'til you do.

TUFTY · 08 July 2010, 13:07

What was the condition of the oil you drained from the unit ?

If it was clear then you may have caused a seal to leak when
you pressurised the oil into the unit.

If it was milky then you possibly already had a leak of some sort, as Nos suggested
Gear shift or drive shaft seal.

If you find this is the case you may as well overhaul all the seals in the leg and fit a new impellor at the same time.

I am currently doing this myself on a 60 yam lower unit.

Hope thi is of some help

Paul

jyasaki · 08 July 2010, 14:24

Hmm. The standard leak-down pressure test for the LU uses (as I recall, and that was a while ago) something like 10 psi which should remain for a period of about 15 minutes. I doubt you'd be able to get that kind of pressure from a tube or bottle pump.

That said, it would be good idea to drop the leg and see where the oil is coming from. Water ingress will enable corrosion which will destroy the insides pretty quickly.

jky

Waz · 08 July 2010, 14:55

Thanks for the replies. The old lube was "Browny Blue" & not "Milky." I had been meaning to change the Impellor anyway but heard it was a bit of a job!?

Waz

Nos4r2 · 08 July 2010, 15:19

Quote:

Originally Posted by Waz

Thanks for the replies. The old lube was "Browny Blue" & not "Milky." I had been meaning to change the Impellor anyway but heard it was a bit of a job!?

Waz

Nah, as long as the lower unit comes off without a fight it's an hour and a half job (that's with me being really fussy and making sure it's all OK in there plus greasing/cleaning it all up for next time and looking at it a lot with a ciggy in my hand)

Waz · 08 July 2010, 16:40

Thanks Nos

Seem to remember somewhere you having problems with lower unit nuts/bolts not wanting to release? Was it a Mercury too? Apart from loads of WD40 or getting someone else to do it, do you have any tips?

Cheers, Waz

Nos4r2 · 08 July 2010, 17:01

Quote:

Originally Posted by Waz

Thanks Nos

Seem to remember somewhere you having problems with lower unit nuts/bolts not wanting to release? Was it a Mercury too? Apart from loads of WD40 or getting someone else to do it, do you have any tips?

Cheers, Waz

Me? Nah, I rarely have problems with them.Last one I had to abandon wouldn't come apart with 2 4x4s in low range pulling it apart (It was mine, ancient and I'd already decided it was scrap by then and thought it'd be amusing).WD40 is a hindrance rather than a help. Don't use it unless it's to free siezed threads. You won't get any to the driveshaft join if the unit won't drop, but everything will be very slippery to add to the problems.

Have a read of this:-

http://rib.net/forum/showpost.php?p=322578&postcount=9

If it won't come off after that, you'll need a pro with a workshop to do it-but it's rare that it doesn't work.

Waz · 09 July 2010, 09:33

Hi Nos

Will have a go this weekend. Thanks for your help

Waz

Waz · 10 July 2010, 13:38

Thanks for your advise Nos, all came away easily.

Few more questions if anyone can help please. Picture 1 shows the Gear Change seal with small slit which must have caused the oil leak. Can this seal be "Picked" out & replaced or do you have to undo what I guess is a nut with two slots?

As the LU dropped, the remants of a seal(s) fell from above but I failed to see from where?
Picture 2 shows this with another small remnant which I don't think was part of the broken seal. My guess is I have damaged or missing seals for where the copper water pipe enters the Impellor housing "Tower". Does anyone know how many seals should be here & if still available? Our local Mercury agents are closed today!

Picture 3 shows a still intact seal where it was found on the driveshaft while stripping

Picture 4, Remnants of a seal at the bottom of the "Tower" on the right ??? Impellor (47-89983) looks pretty good but of course will still renew.

Picture 5, Bottom of "Copper" pipe just visible

Many thanks - Waz