My manual for a 1976 40hp with the split gearcase says to apply adhesive to the groove in the skeg. After install seal. Then apply adhesive to the upper gearcase and around the screw holes. Then it says to dip screws in gasket sealer.
The tightness of the screws is the primary seal. Screwhead jammed up so tight against the aluminum there is no room for leakage. That's why they are so #&%** tight as originally installed. Scotchgrip #847 is the correct sealant. Not to say other stuff won't work. But yes, put some on the screws.