How Much Gear Oil

l008com

Senior Chief Petty Officer
Joined
Jun 14, 2007
Messages
730
I have a 90 HP 1989 3cyl 2 cycle Mercury outboard.
I'm pretty sure I was told in here that my engine takes about a quart and a half of gear oil. The guy at West Marine told me the same thing, which is why he sold me two quarts (this was last year). So I just changed the oil for the first time (first time I did it, not first time it was done) and everything went well. Except the oil started pouring out the vent screw after less than one quart. Maybe something like 24oz of oil. I let it sit for a bit, then slowly pumped a little more in, but it came right out. Is everything ok? Did people just get my capacity wrong? Or is there something wrong with my motor?
 

l008com

Senior Chief Petty Officer
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Jun 14, 2007
Messages
730
Re: How Much Gear Oil

18oz is how much oil it took, and not a drop more.
 

minuteman62-64

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Apr 12, 2011
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1,350
Re: How Much Gear Oil

My 30 HP takes about 6 oz. I assume a 90 would take more - but a quart and a half? That is 48 oz. Seems like a lot.
 

minuteman62-64

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Re: How Much Gear Oil

It occurs to me that one of the joys of our system of weights and measures is that its easy to make a mistake when converting units. For example if the person at West was in a hurry and was thinking 12 oz. per quart (I've done it more than once) he'd easily read 18 oz. in the specs and come up with a quart and a half as the amount needed.

12, 16 and 32 can easily get used in the wrong application if one is in a hurry.
 

l008com

Senior Chief Petty Officer
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Jun 14, 2007
Messages
730
Re: How Much Gear Oil

So I just drained this out of my boat. It's 1 year old. Is that "cloudy" oil, that would imply a seal leak? Or is that just regular dirt streams in the oil?

img2485b.jpg
 

GA_Boater

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May 24, 2011
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49,038
Re: How Much Gear Oil

Do you have a magnetic drain plug with "fuzz" on it? How long since you used the boat? Maybe some separation of stuff if it's been idle for a while. Pour the oil in a clear container to see of there is water on the bottom.
 

l008com

Senior Chief Petty Officer
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Jun 14, 2007
Messages
730
Re: How Much Gear Oil

The boat has been sitting all winter. And yes the drain plug does have a magnet on it, i didn't notice very much fuzz on it. I already poured the oil back into the dark container it came from and disposed of it.
 

GA_Boater

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49,038
Re: How Much Gear Oil

I guess the best you can do now is run it a few times and drain the oil again. Just check for water the next time.
 

TD_Maker

Chief Petty Officer
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Aug 31, 2005
Messages
564
Re: How Much Gear Oil

It will take slightly less than 1 qt. Be sure you let the lower unit drain completely before refilling.
 
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