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BF225 - Ugh. Wrong gear oil...

brettmarl

brettmarl

Regular Contributor
Crap... I think I just realized I used the wrong gear oil in my lower units.

I put this stuff in:

Mercury SAE 80W-90
https://onlineoutboards.com/products/mercury-gear-lube-sae-80w-90

I meant to buy the Mercury High-Performance SAE 90.

As I'm cleaning up my shop - just noticed on the bottle of the 80W-90 it says "For use in all outboard lower units and jet pumps below 75 hp except outboards with electric shift gears".

I've probably only done 1-2 hours on the motors with this in. Obviously I should pull the boat and replace, but then I just read this:

"NOTE: Mercury Premium SAE 80W90 Gear Lube should not be mixed with Mercury High-Performance SAE 90 Gear Lube."

Couple of questions:

1. any possibility I did damage for the short runtime?
2. Does the "do not mix warning" mean - don't use a blend of both? If I empty, fill with SAE-90, dump it all to flush and fill again, am I in the clear or is trace-stuff mixed a bad thing?

I self-nominate for the dumb-ass of the week award.
 
1. No damage unless you were towing a barge for those 2 hours! Even then, probably not.
2. I would just drain what you have and fill it with the High Performance.
Flushing it once would work too.

I wouldn't be too hard on yourself. I've found their naming confusing.
Premium sounds like it would be the good stuff. I've bought it by mistake before.
I often just use automobile synthetic 75W90.
 
When I had about 600 hours on my BF 225 I did exactly the same thing you did. But didn't realize it until about 200 hours later. Switched over to the High performance Merc 90 at that time. Apparently no harm done. I'm approaching 2200 hours and no lower unit problems that I'm aware of.
 
No. I just drained it real well, changing the tilt several times to get as much out as I could. Let it drip out over several hours while I pulled maintenance on other stuff.

These lower units are really tough, and once broken in properly, they tend to perform well for long periods of time. On my 2007, the original seals have never been broken after 2100+ hours. I just check it every 100 hours and replace the gear lube every 200 - 300 hours.
 
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