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Year

How often lower unit gear oil chg. on Merc 40HP?

Heinz Just curious - I just chgd. lower unit gear oil - cheap and easy on my 40 hp Merc, how often should I do this? I want all to last as long as possible. Is it OK to use automotive 80/90 wt. like in my vehicles diffs - I have gallons of that? Thanks, Heinz 2002-05-19
fishthebay I would only use specified lower unit gear oil. Quicksilver is what is recommended for your Mercury. You can pick this up at your local boating store for about $8.00 a quart.

It is recommended that a minimum of each boating season the lower unit oil is changed. I do mine more often - like 2-3 times per season. I run by boat 10 months a year.

Hope this helps. Don't be cheap on this, because it will cost you in the long haul.
2002-05-19
Mumblerone In upstate NY you must do at least once a year BEFORE winter. The reason BEFORE winter is that if any water gets in during the season it will freeze and crack the lower unit for sure during the winter. If it's milky during the season it needs to be changed, water is in the gearcase, should repair seals. Other than that once a year has always worked for me. [Wink] On the OIL thing, I would stay with marine stuff. I have used 90wt Gear lube in the past...but always felt some additive was left out. Use Marine Grade! 2002-05-19
Trent Crawford Yes you can use as you say "automotive" Use the "Hypoid" type.

There are three API service categories for gear oils:
* API GL-1
* API GL-4
* API GL-5
Most outboard manufacturers recommend API GL5 gear oils for their lower units. API GL-5 gear lubricants are for both mechanical shift units calling for Type B gear oil and electrical shift mechanisms calling for Type C gear oil. (only the viscosity value will be different for each application)
2002-05-19
Heinz Thanks all for the hints! Heinz [Smile] 2002-05-19

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Outboard Motors

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