'86 Mercury 45 (Classic 50) lower unit oil...

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Apr 24, 2007
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Didn't feel like shopping so I drained then filled with Mobil1 75/90 LS GF-5 gear oil. Wondering if it's ok
the almost empty 'Marine' tube I had read 80/90 GF-5 so I figure it's pretty darn close.
 
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been 4-5 yrs since I did that, oil came out black..don't fish like I used to just leave her tied on the dock all year.. I've owned this since new 34yrs.

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That gear lube should be fine.

If the lower unit sits in the water all summer you should be draining and refilling with fresh gear lube when you pull it out for the winter.
 
Should be fine. I've always run the lower unit lube just because it claims to have an additive in it to help disperse the water, but not sure how necessary it is.
 
lower unit is tite, oil came out black but no water. never had a lower unit issue and I've operated all the way into frigid ice breaking...i do have a head scratching problem with water fouling the inboard fuel, seems if it gets loaded with rain the tank will take on a quart or so of water but not always...sometimes I'll start and run as I pump maybe that is the problem once a vacuum is established...it's all under the 34yr. old deck and I dread the thought of going there....the joys of owning a old tub.
 
So, the fouled fuel issue...I'm going to solve it without fixing the actual problem under the old deck...bought a automatic bilge and a solar trickle charger that
I can stow when running...presto!... no water build up, no fouled fuel..love a old tub plan.
 
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