On these engines the main thing is to not use a low viscosity automotive oil like 5w/30 or 10/30. You can use straight weights like straight 30, or 40, a 20w/50 or you also can use the Mercruiser/Quicksilver 25/40 or the 15w/40 used in both diesel and gas engines. The idea is that marine engines spend a lot of time at higher RPMs than would be typical in an auto or truck engine so you don't want an oil that might thin out and lose viscosity.
As far as the outdrive, I have head that the Volvo cone clutch drives do better with their gear oil, but I've had no experience with them.
I use the Merc/Quicksilver 25/40 in the engine and the Merc High Performance gear lube in the outdrive. Good results with both.