We used to use OMC HPF gear case lube in our OMC Cobra sterndrive but can't find it anywhere around here now. The closest thing is Quicksilver High Performance lube. Is this a suitable substitute or is it not compatible?
A lot of places use the green Merc stuff in all drives. I've never had a customer with a problem as a result. Make sure you get it all the way into the upper drive.