Water in Gearbox!!!!!

bryan160

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26 Nov 2006
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Hi, The gear oil on my Mercury outboard is slightly creamy in colour, think this is caused by water in the oil, is this a problem that I must sort, or is it not that much of a drama??

Cheers Bryan
 

Norman_E

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Creamy colour indicates an emulsion of oil and water. Best to drain it out and replace with oil, as the emulsion will not be as good a lubricant because it will not withstand being squeezed out by the pressures between gear teeth so well as oil designed for that purpose. It does not take much water in the oil to create the creamy mess as the gears churn up the mixture, so finding the cause of the water ingress may not be easy. Unless the leak is obvious it may be best just to replace the oil, keep an eye on it, and accept that you will have to do oil changes every so often.
 

VicS

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Yes it is caused by water as Norman_E says. Do as he says change it, making sure you drain the old oil thoroughly (overnight perhaps). Even consider flushing it with a charge of engine oil with a short run in a tank to stir things up and drain thoroughly before refilling with the correct oil. I suggest engine oil because it a whole lot cheaper than the gear oil (EP90 ?) and being lighter it will clean it out better than gear oil.

Then keep an eye on it. One thing for sure though it wont cure itself but you may decide that there is no need to panic.

Ultimately you will need to change a seal. It is almost always the seal on the prop shaft that goes as that collects all sorts of rubbish, like fishing line. I dont know about Mercurys but you may find two seals back to back, one keeps the oil in and the other should keep the oil out, it may be all one assembly though. If two its the outer one that goes but IMHO its worth replacing both.

There are other seals of course. On the drive shaft at the top of the gear box and on the gear selector shaft but they require much more work and know how to replace. Go for the prop shaft seal(s) as changing them is usually fairly straightforward.

If you told us the model maybe someone will be able to offer detailed advice on changing the seals. If not then the iBoats forums are a first class source of info on outboard problems. You'll find a forum dedicated to Mercury and Mariner engines. If you go there be sure to quote the full model details ie HP, year, model and or serial numbers
 
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