changing gear oil - 1967 Merc 500 50HP

[livesforvacation]

I have a 67 merc 50hp and i need to change the lower gear lube oil. Looking for help on making sure i choose the right product to use as well as some high level instructions on how to go about the change in this unit. I know there are a couple of plug screws to remove, but am looking for some high level instructions so I go about doing it the right way.

thanks
John

 

[robert graham]

Remove drain and vent screws....drain old oil into a container....screw in hand oil pump threaded fitting into drain opening....pump until oil comes out of upper vent screw, replace upper vent screw, remove pump and replace drain screw.....Walmart carries these hand pumps for about $8.....may want some new washer/seals for the drain and vent screws....there's just not much to this job....keep some rags handy to clean up any oil...

 

[racerone]

If any water is present in the oil you need to look at resealing the gearcase.-----Now if this is an original unit it will have a carbon steel driveshaft and not stainless.----They are usually corroded right where the oil seals sit on them.

 

[Chinewalker]

Keep in mind - the VENT screw is the small slotted screw near the AV plate, NOT the larger slotted screw above the AV plate - that is the flush screw that access the water pump. The drain screw is the dime-sized slotted screw at the head of the bullet.

As racerone noted, those 1960s era Mercs are prone to shaft rust. For whatever reason, Mercury was very late to the stainless shaft game.

 

[livesforvacation]

thanks for the tips! My buddy helped me out and we got the job done.