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Lower unit gear oil possible aeration?

I

iaff284

Contributing Member
I have a 1995 Crownline 225BR with a Mercruiser 350 Mag coupled to an Alpha Gen 2 drive. I noticed after several days of boating that the gear lube in the lower unit reservoir bottle was butterscotch colored. It is Pennzoil brand lower unit gear lube and is golden in color when new. I replaced the impeller and changed the lube this spring and honestly after checking the level after the service I hadn't paid any attention to the color of the lube after we ran the boat a couple of times. I initially was concerned that there was water in the lube, but after four days of sitting on the trailer the lube looks the same with no seperation in the bottle. I cracked both the bleeder and fill screws and the same color of lube came out with no water present. There was never any oil slicks on the surface of the water by the drive at any time. The level has never changed in the reservoir. I searched on the forum and have found suggestions that the oil may just be aerated and that the butterscotch color is completely normal. Just wanting to confirm that this could be normal, that four days is long enough for water to seperate out of the gear lube, and if there is anything else I should check before I smoke my lower unit.:confused:
 
Thanks for the info....I was just concerned about the possible water intrusion. I share the same thoughts in regards to pennzoil, but in east central illinois, oem gear lube is not easy to find. On the next service I am switching back to Merc High Perf Lube.
 
I believe the Alpha Gen 2 and the Bravos have the reservoir bottle mounted on the engine. There is a trim cylinder reservoir but its on the base of the pump.
 
All gen 2's have the resevoir plastic bottle at the engine. The oem gaskets for the outdrive have an extra hole where the spring loaded valve goes. If the oil was golden brown and appears milky I would suggest water.

If it is water getting in the drive maybe one of the drain/vent plugs seal/ orings is bad and water is getting in.
The only way to properly check is to drain outdrive. Remove out drive. Pressure check to 15 psi and it
Should hold for two minutes. Next do a vacuum check and it should pull about 8 -10 inhg and hold for two minutes.

This is the only way to be sure!!!!
 
2X on the pressure test...

The other thing to remember about water intrusion....oil will float on top of the water so it isn't always visible
 
yup, let the boat sit over night, remove the Drain plug and see what comes out. I'd also think about pulling the prop and make sure you don't have a peice of line wrapped around the prop shaft.
 
I'm not quite understanding how some of you believe that hydrogenated oil will separate from the water in several days.

I've removed water contaminated gear oil long after several days, and it has usually remained hydrogenated.
Thank God that it does remain hydrogenated for as long as it does, otherwise we'd see more lower unit gear and bearing damage from rust.

Just my two cents.... I'm open to comments. :D

Back to the reservoir for a moment.
The beauty of the reservoir, is that it helps prevent the otherwise pressure differential from warm to cold, as a drive heats and expands, and as it cools and contracts.
With the older drives minus the reservoir, if pressure pushes oil past a weak seal, it may also pull water back in upon cooling down.

I do agree.... do a pressure/vacuum leak down test. The longer it will hold, the better, IMO.
Turn your shafts while doing the tests.


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