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Old 23 July 2014, 06:40   #1
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Water in lower unit ?

Hi guys, just got our engine out to give it a service before using.
We bought it 2nd hand and have not yet used it.

So began by draining the lower unit oil, there was some white in the oil which I believe indicates water, so let the oil sit over night to see if the water would seperate and float on top.

Have added a photo, is this oil normal colour for being old, or is there water in, meaning a seal or seals need replaced ?


I'm just wondering if a small amount of white is normal after being in there a while ( at least 2 years ) caused by condensation etc ? or is there definately a seal leak ?

What would be the next most logical step ?

I also wish to change the impellor, is this easily done by yourself or is it specialist job ?

I have a reasonable set of basic tools, mostly repair our own cars etc..

Would like to take it to the local marine workshop but the prices are pretty high so would rather attempt it myself first if it is do-able, or do i bite the bullet and shed out the hard earned cash !??
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Old 23 July 2014, 07:40   #2
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Water in lower unit ?

I wouldn't worry about that oil, looks ok in the picture. It's certainly not badly contaminated. Like you say, it may just be a little bit of condensation water.

Fill with fresh oil and replace the washers behind the drain/fill plugs. Next time you drop the oil dry and do it into a tray, I find it easier to spot the water when the oil is spread over a wide area than in a full jug.

If you are confident at all with spanners then the water pump is easy enough.

When I get an engine with an unknown history I usually give it the works. Plugs, stat, water and fuel pumps and oil change with new washers. When replacing the water pump I usually replace the cup too, not just the impeller then whip prop off to check for fishing line/debris around shaft and grease the splines.
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Old 23 July 2014, 08:35   #3
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Unbeknownst to me the lower unit on my engine was running with only water in it. It ran well and no damage was apparent when it was taken apart to be repaired.

It also drained a lot quicker than oil does!
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Old 23 July 2014, 08:43   #4
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Hi Alan, thanks for the quick reply. I drained it into a flat tub but then just poured into the bottle to see any water seperation better.

Here is a photo of the remains in the flat tub, and also the base of the bottle, white milky sludge.

Does this still look ok ?
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Old 23 July 2014, 08:51   #5
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Hugh, was the engine run in fresh water or salt ? You seem very lucky !!
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Old 23 July 2014, 10:18   #6
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Checking the LU for leaks generally involves slightly pressurizing it and seeing if it holds the pressure. Not rocket science, but takes some specialized fittings (generally a threaded adaptor into the fill port, with a gauge and a handpump sitting off of it.)

If I remember right, I think Yamaha specified about 3psi (definitely verify that before trying.)

jky
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Old 23 July 2014, 11:15   #7
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Yep you have some water contamination in there alright, could be down to dodgy seals or something simple like bad washers if they weren't replaced after last oil change.

If it was mine I'd fill it back up with fresh oil, put new washers on, put a few hours on it and check the oil again, if you leave the oil to settle overnight in the gearbox and check the next day any water should be at the bottom of the box and be the first to appear when you open drain plug.

If water was present I'd be digging a little further in to the problem.
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Old 23 July 2014, 11:27   #8
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Guys,

Surely the water will be emulsified into the oil and won't settle out?
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Old 23 July 2014, 11:33   #9
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It does to an extent, with light contamination itl settle to the bottom as a milky yellow fluid, heavy contamination you find ALL the oil is a milky yellow fluid.
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Old 23 July 2014, 11:50   #10
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Quote:
Originally Posted by Searider View Post
Guys,

Surely the water will be emulsified into the oil and won't settle out?
Yep, spot on. The gear oil is designed to combine with the water, so even if water gets in, the oil will still do its job. It wont settle back out.

I wouldnt start worrying about yet, lots of engines never have a gear oil change. I recently serviced a friends early 80's Yamaha that still had original oil in it

But its a really important job, Dad trashed the lower end of a nearly new Yamaha 90hp when I was a kid, when a oil seal failed and the contents of the gearbox became more water than oil
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