Oil in my 68 Merc 500

[Cpt Brad]

Just bought a 1968 Mercury 500 four stroke. I want to change oils before running it but I can't find a drain plug, dip stick or fill hole. Also on the bottom end I don't see a drain. Where is the water pump impeller? Where could I find a good maintenance manual? Any help would be greatly appriciated

 

[hotrod53]

A 4 stroke Merc 500 in 1968, are you sure about that???? 4 cylinder maybe, 4 stroke.. I've not seen one.

 

[racerone]

A 4 stroke MERCURY [n 1968 would be a special motor.

 

[Chinewalker]

It's a 2-stroke - you mix the oil with the gas. There is no sump.

That said, there IS oil in the lower gear housing. To drain that, you'll need to remove the dime-sized slotted screw at the fore of the gearcase bullet, plus the round-headed pencil-eraser size screw up near the horizontal plate above the propeller. The upper acts as the vent for the lower. To refill, use 90-wt. outboard lower unit oil and fill from the bottom until it comes out the top. Place the top screw back in the hole to act as a stopper so you can replace the bottom screw without having all that oil dribble out all over your hands...