Well, I have used Lucas in both of my BMWs I have a 1993 318is with 396,520 miles on it and a 1994 840ci with 200,000 on it. I use the oil stabilizer. I have heard people comment about it foaming and such. I have never had a problem with it. If it did do what these people claim then the company would be out of business due to bad publicity and broke.
I don't think that Lucas would say the stuff could be used in an outboard lower unit if it had not been put through some tests to determine whether it could stand up to the rigars of the drive itself. My only concern was the water issue. If I ever did get any water in my lower unit, does this oil mix with water to keep my gears from turing into mush? Rebuilt lower unit...$1400.00.
I do know some guys who use Lucas in their drives, and seem to be happy. All the research I have been doing...I have read that AmsOil is the way to go. Full Synthetic. Some people report about 200 more RPMs. Gonna run the Lucas for a while then, flush out the unit and fill with AmsOil. ....Dirk