I have a 496 Merc Mag Ho and need to know what weight and how much oil this motor needs? And on the motor where is the sea water pump...I want to replace the pump or just the impeller in it...
Also a TRS out drive and need to know what type and weight of gear oil it needs? Also the Velvet drive wieght and type...thanks if it would be easier you can email at [email protected]
I would have these answers but I don't have any of the owners manual due to the previous owner lost them.

Use Mercury 25W-40 synthetic blend and change every 50 hours.

The water pump is on the very bottom of the block on the starboard side of the engine. You shouldn't need to change the pump unless the previous owner damaged it, impeller runs around $40 bucks.

8 qts on a drain and refill, 25-40 merc oil here, also if you are thinking of doing the impeller look into the hardin marine stainless, the stock brass pumps are junk if they are grooved out