Lower unit lube replacement

[kvjimbo]

The manual states to fill until fluid comes out of the vent hole and then remove ~ 1 oz. to allow for expansion. My mechanic doesn't recommend removing 1 oz. of fluid because he believes filling to the top helps keep water out.

Any recommendations?

 

[jimmbo]

Re: Lower unit lube replacement

Hmm, engineers who designed the motor say one thing, a mechanic says another. Well, if there is air in the case for expansion, as the fluid heats up and expands, the air compresses. When the fluid cools and contracts the air decompresses. If the case is full and there is no air in the case and the fluid heats up, being noncrompressable it has to escape the gearcase usually blowing out thru the seals. Now when the fluid cools, it contracts and with no pocket of compressed air inside, a negative pressure will form inside the gearcase, quite likely pulling water into the case thru a weakened seal. I would insist the mechanic follow what the manufacturer states.

 

[Chris1956]

Re: Lower unit lube replacement

You guys miss the obvious. When filling the gearcase, some air will always remain. There will always be some air at the very top of the gearcase, and when you pull the filler tube some gearlube always leaks out before you can get the plug in. The mechanic therefore desn't need to drain 1 oz of gear oil, as it has already leaked out, or was never put into the gearcase.

 

[Cricket Too]

Re: Lower unit lube replacement

Exactly, no way you are ever getting a gear case completely full of oil. I usually give another pump after I put the plug back in the vent hole to make up for what is lost when I pull the filler tube off the bottom.

 

[jimmbo]

Re: Lower unit lube replacement

If mercury says to drain an ounce of oil I'm sure they had a reason.

 

[chum1]

Re: Lower unit lube replacement

If mercury says to drain an ounce of oil I'm sure they had a reason.

Yea:

Merc Rep: "So you want us to fix your lower end seal problem for free?.....lets look at manual....um says here to drain one ounce of oil. Did you do that?"

Customer: "Yep"

Merc Rep: "Sorry indications from manual show your sol, have a good day."