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Author Topic: Lower unit leak?  (Read 570 times)

Offline Angry Perch

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Lower unit leak?
« on: November 24, 2020, 04:37:19 PM »
Bought a new to me boat with a 2005 (I think) Mercury 15. Noticed a small wet spot under the motor after sitting for a couple weeks. looks like it weeping out of this hole. Any ideas?


Offline Sitka_Blacktail

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Re: Lower unit leak?
« Reply #1 on: November 24, 2020, 05:37:47 PM »
Check your gear lube. That's the drain or fill hole, isn't it? If water is leaking out you probably need to drain it and add new oil and get a new rubber washer for it as the old one appears to be leaking.
A man who fears suffering is already suffering from what he fears. ~ Michel de Montaigne

Offline Stein

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Lower unit leak?
« Reply #2 on: November 24, 2020, 05:57:21 PM »
Drain hole is on the bottom, either in the middle of the skeg or behind the prop (depending on the model/year), fill hole should be above and to the right of that.  I am guessing, but my guess is that is a port in the the water cooling system.  The oil will be below that hole for the most part so gravity won't pull it out.  Was there oil coming out of there?

For the lower unit, just pull the drain plug and see what comes out.  Usually, water leaks into the lower unit, not oil leaking out since there no pressure in the lower unit so nothing to force oil out when it's sitting there.  Oil is less dense than water, so if you have water in the lower unit it will come out first.  Either water will come out or milk shake stuff if you have ran it lately.  If it looks like regular oil you are fine.

If it's water or milk shake, pull the prop shaft and look at the gears.  If it's fresh water or you catch it early you could be lucky as it takes some time for the gears to go since they are bathed in pretty heavy oil.
« Last Edit: November 24, 2020, 06:54:27 PM by Stein »

Offline jay.sharkbait

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Re: Lower unit leak?
« Reply #3 on: November 24, 2020, 06:08:27 PM »
I think that's a water drain hole for the exhaust passage. Its meant to prevent water from freezing and causing damage.

Its probably residual 2 stroke oil or the engine was fogged recently.

Offline Angry Perch

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Re: Lower unit leak?
« Reply #4 on: November 25, 2020, 08:38:42 AM »
I'll have to take a closer look next time I'm over there.

Offline scotsman

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Re: Lower unit leak?
« Reply #5 on: November 25, 2020, 09:34:48 AM »
Just fyi, those 2 stroke Merc 15ís are great motors.

Offline Angry Perch

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Re: Lower unit leak?
« Reply #6 on: November 25, 2020, 10:04:34 AM »
It's a 4 stroke.

 


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