TOPIC: mark 58 lower unit oil change

OK, did I screw up??
Months ago I drained the lower unit oil in the Mark 58, came out black and gunky. Now I have the motor put together and painted up real perty and want to put new gear oil in the lower. As I am an old OMC person I removed the "flush" screw on the upper portion and proceeded to pump the lube in the lower fill hole waiting for the oil to come out the upper hole, didn't happen. Oil started coming out the lower fin/drain so I pushed past a seal somewhere. Obviously there's enough oil in the unit now What's the proper way to fill these sweethearts? Or was I right and there is something plugging up a passage that needs to be flushed?
Cal

First of all they take grease not oil from the factory.
remove the drain plug.
remove the small screw below the cavitation plate(grease vent)
put GREASE in from the bottom till it comes out the vent
install the 2 screws finished
i use lubriplate 105 or john deer cornhead grease.

Thank you, I'll get the grease. Is it a light weight stuff that gets pumped in and drain the 90 weight.

lubriplate 105 squezze from the tube.2 tubes will be more than enough.drain oil then fill with grease and push some extra out to get left over oil out.

63 Sabre wrote:

OK, did I screw up??
Months ago I drained the lower unit oil in the Mark 58, came out black and gunky. Now I have the motor put together and painted up real perty and want to put new gear oil in the lower. As I am an old OMC person I removed the "flush" screw on the upper portion and proceeded to pump the lube in the lower fill hole waiting for the oil to come out the upper hole, didn't happen. Oil started coming out the lower fin/drain so I pushed past a seal somewhere. Obviously there's enough oil in the unit now What's the proper way to fill these sweethearts? Or was I right and there is something plugging up a passage that needs to be flushed?
Cal

The "FLUSH" has NOTHING to do with the oil in the unit. It is a direct path to the waterpump and is for a threaded fitting that hooks up to a garden hose for flushing a motor after running in salt water.

You need to fill from the bottom "DRAIN" screw until it comes out the vent screw - which will be a small (usually) round head screw. I believe it is either just above or below the AV plate, at a bit of an angle.

Also, you may want to consider using grease in place of oil as most of those old shafts are pitted enough that the oil simply leaks out...

- Scott

Scott, thanks for clearing some things up. I admit I was a Merc neophite and when I searched the lube on google all I found were directions for the newer engines which lube up like an OMC. Nothing on this site search about changing the lower unit lube in the older Mercs, now I know. I'm going to the local Fleet Botique to pick up the corn head grease. There is a great video on Youtube about that stuff. Might be worth a look by everyone who runs these motors.
Cal

Having a hard time finding the grease in my area, even the local farm stores never heard of it, of course all the sales reps are youngsters. The local Merc dealer says the don't use the grease anymore and just fill the older lowers with 90W gear lube.

try a auto parts store for lubriplate 105. now galled assembly grease and not lower unit grease.
eastcoastmarine.com has it.
check ebay for it and john deer cornhead grease.

Yes i found both on Ebay.

Hey Sabre, Don't feel bad. I wish I would have read this earlier today. I too removed the drain plug and the flush plug, they are the same size. I thought I had problems because the top plug had water that never drained into the oil drain can. Mine was filled with 90 weight too. Sure takes a while to drain with the vent screw in. We all live and learn.

Hey Sabre, Don't feel bad. I wish I would have read this earlier today. I too removed the drain plug and the flush plug, they are the same size. I thought I had problems because the top plug had water that never drained into the oil drain can. Mine was filled with 90 weight too. Sure takes a while to drain with the vent screw in. We all live and learn.

Found the corn head grease at a local contractor supply dealer that sells and repairs JD heavy equipment.