Black oil in lower unit

Chester · Posted: Sat Mar 31, 2007 2:43 pm Post subject: Black oil in lower unit

I have twin '05 Honda 40's with about 30 hours each. The dealer told me the previous owner had the 20 hour service performed. While changing the oil in the lower units the oil from the port engine looked nearly new. Not so the starboard side, that oil was very dark, looked more like used engine oil.
Opinions please!

Larry H · Posted: Sat Mar 31, 2007 2:55 pm Post subject:

Milehog,

Did the dealer change the gear oil at 20 hrs? If so, why are you changing the gear oil at 30 hrs?

If the oil came out black at 20 hrs, the dealer should have looked for a problem, which would be under warranty.

Water in gear oil normally makes the oil look like a milkshake. Black oil would indicate burned or overheated oil, both are unlikely in a lower unit(they are water cooled!), however a bearing failure could overheat the oil.

Did you ask the dealer what the color means?

Chester · Posted: Sat Mar 31, 2007 3:42 pm Post subject:

Spoke with a mechanic at the dealer. His over the phone diagnosis? He suspects that the starboard engines lower unit oil change was missed during the 20 hour service. The oil did not smell burnt.
Is it normal for used lower unit oil to get dark after use?

Larry H, I changed the oil 'cause the manual calls for service at 6 month or xx hour intervals.

thataway · Posted: Sat Mar 31, 2007 5:32 pm Post subject:

At 30 hours the lower unit oil should look clear.

Larry H · Posted: Sat Mar 31, 2007 9:50 pm Post subject:

Milehog,

I agree with Bob that the oil should look like new in both lower units at 30 hours.

I would recommend changing the oil now and check it again at 50 hours or so.

Look for metal particles in the drained oil and if the drain plug has a magnet on it look on the magnet for metal. A small amount of metal is normal, especially for a new gearcase.

The factory break in oil may be different than the oil used at the dealer so it could look different.