Took the lower unit of my B1 off awhile back. When we put it back on it had a small leak. I forgot and took the boat out Sunday, when I checked all the fluids before leaving the dock I noticed the drive oil was low. I added fluid and decided to proceed. The boat ran great for about an hour then I heard a humming at speed. I pulled the throttle back on the left drive and the sound went down. At idle the sound was gone. When I parked the boat there was milky oil leaking out of the left drive. Water got in the lower unit I suspect, what do you think the humming sound was? Where should I start to ensure everything is checked?

I would pull the drive and have it checked & re-sealed.

D. Ocean
Pompano Beach, FLA

ya why wait till it blows up and costs 1000s

Just the lower, or the whole drive?

The whole enchilada.

D. Ocean
Pompano Beach, FLA

If it's noisy the damage is already done pull it teait down and replace all worn bearings you'll most likly find most of it in the upper gear box

I agree. Tear it down now while the gears may still be ok. Bearing are most definatly gone.