Gear lube change with reservoir question

[tacx]

Alpha 1 gen 2. With gear lube reservoir.
When draining the gear lube from the outdrive I am assuming that the lube reservoir also drains out?
Standard refill is to fill from the drain hole until the lube comes out the vent hole and then install plugs, and then add lube to the reservoir..

Why can't one fill from the drain hole until the lube reaches the reservoir?

 

[harringtondav]

That is what I do. I fill from the bottom drain until the lube oozes from the vent. Then I replace the vent plug and continue pumping lube until it rises into the reservoir bottle. Then I top off the reservoir. I believe this chases more air out of the closed system. I keep the vent hole open so I know how close I'm getting to filling the drive. It seems to take forever to get the lube up that far. Not too many more pumps to get it pushed up to the reservoir.

After a lube change, the lube level in the reservoir will drop after a few hrs. of use. This is normal. Air is trapped above the lube check valve in the upper hsg. With heating and cooling, the check valve in the reservoir cap eventually allows reservoir lube to replace some of that air. The lube level in the drive will rise above the check valve, and the level in the reservoir will drop accordingly.

 

[tpenfield]

It has been a while since I read through the gear lube procedure in the manual . . . but IIRC, the prescribed procedure (at least for Bravo outdrives) was to continue filling gear oil from the bottom after you replace the top plug until you have some gear oil reaching the reservoir. Then you can fill the reservoir directly, as needed.

So, nothing wrong with what you are suggesting.

 

[tacx]

I didnt know there was a check valve in the lube line ? If there is, then how can the lube flow in both directions?

 

[harringtondav]

The check valve is between the bell housing and the drive. It's open when the drive is installed. It closes when the drive is removed to keep lube in both the drive and the reservoir.

 

[tacx]

AAH, now that makes sense. Thanks for clearing that up for me.

 

[JackBronson]

What harringtondav wrote: That is what I do. I fill from the bottom drain until the lube oozes from the vent. Then I replace the vent plug and continue pumping lube until it rises into the reservoir bottle. Then I top off the reservoir.

THIS is exactly what the Mercury manual says to do. Read the procedure just this past week.

You can save time by dumping the reservoir out before you drain the drive. But you must fill the whole system from the bottom in order to push out the air.

 

[tacx]

Thanks, The check valve thing had mestumped.