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how come my used gear oil looks different?

brettmarl

brettmarl

Regular Contributor
2@BF225's. Port has 125 hrs, Stbd has 555 hrs. Last gear oil change was 100 hrs ago. Using Merc SAE-90. Stbd comes out 'well loved' and black, Port looks like it did on the day it went in.

Port also had maybe 1mm layer of shavings on plug which seemed insignificant and I assume normal for a newer engine settling in. Stbd plug was clean.

Wouldn't you expect port gear oil to be the same as stbd? Or is the dark stbd color bad-mojo?

oils.jpg
 
Last edited:
brettmarl said:
2@BF225's. Port has 125 hrs, Stbd has 555 hrs. Last gear oil change was 100 hrs ago. Using Merc SAE-90. Stbd comes out 'well loved' and black, Port looks like it did on the day it went in.

Port also had maybe 1mm layer of shavings on plug which seemed insignificant and I assume normal for a newer engine settling in. Stbd plug was clean.

Wouldn't you expect port gear oil to be the same as stbd? Or is the dark stbd color bad-mojo?

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I don't see any milkiness, so I would only assume its because of the hour usage between the two. 500 hours is a good amount for that small amount of oil to endure in my opinion, the other motor is working harder to push a boat that requires 2 engines to push it effectively, so in my opinion it is not without question that it should be that color given it has 430 more hours or 4 times the amount of run time than the port.

Flip your scenario next cycle and run the port 555 and starboard 125 and then change the oil. I don't think in my opinion you have anything to worry about.
 
Sorry - maybe my first post wasn't clear. The engines have 125/555 TOTAL hours, but both gear oils were last changed ~100 hours ago (108 to be precise) in May (less than 3 months ago). I swapped fluids in both at same time and always run both engines together. Honda manual says to change motor-oil and gear-oil every 100 hours.

Changing every 50hrs with SAE-90 seems excessive and means I've have to pull the boat once a month! :)

From what I've gathered googling around, some people say black gear oil is normal as it breaks down with heat, others say it always comes out the color it went in. I've also read that black oil can be a sign of running too hot and breaking down quicker due to bearings being out of tolerance.

Just strikes me as odd that two identical motors with the same oil and same change-interval are showing different results.
 
With 108 hours, the gear oil should not be black. It should come out about the same color as it went in, just a little dirtier. If you didn't get metal shavings on the magnetic drain plug, I doubt if you have a gear alignment problem. You've got some other problem going on. I'm not sure what. Did you smell the black oil? Does it have a different smell than the clear oil? Does it smell burnt?

These 200/225 lower units are really rugged. At close to 2200 hours I've never had to touch mine except to change the oil, change out props, and replace water pumps.
 
I didn’t notice any obvious smell at the time but didn’t think to sniff it up close... now it’s all mixed in with the motor oils ready to recycle. I’ll check that if it comes out black again.

I spoke to my Honda Dealer and they said “yeah we sometimes see it come out black. As long as no shavings or water you’re all good.” Which wasn’t a very satisfying answer. I don’t like anomalies ;)
 
Your Honda dealer is correct, some lower units burn the oil over time and some don't. I have seen oil come out like that after 50 hrs , as long as there is no metal filings it's not a problem
 
Not 100% sure Bill, probably to do with alteration of tolerances as it wears, it applies to all makes, not just Honda
 
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