V-8 Lower unit oil change

[Old hurst]

Don would you please repost the correct lower unit
fill procedure? I can't seem to find it. Thanks
S/N 3B268926

[EuropeanAM]

Level Gearcase. Fill from bottom to top vent plug.

Raise trim for 2 minutes, rotate propshaft.

Level gearcase. Fill from bottom to top vent plug.

Repeat above until the level is AT the vent opening when you come back to LEVEL.


(The key here is that you're ensuring that gear lube is migrating all the way up into the forward cavity of the gearcase, resulting in the correct LEVEL when the gearcase is LEVEL).

[Pulsare2020]

Level Gearcase. Fill from bottom to top vent plug.

Raise trim for 2 minutes, rotate propshaft.

Level gearcase. Fill from bottom to top vent plug.

Repeat above until the level is AT the vent opening when you come back to LEVEL.


(The key here is that you're ensuring that gear lube is migrating all the way up into the forward cavity of the gearcase, resulting in the correct LEVEL when the gearcase is LEVEL).

I can vouch for Don's fill procedure. I was able to get 2 - 3 ounces more gear oil into my TM2 lower unit following Don's procedure, versus keeping it level and filling it until the gear oil ran out of the top plug.

[Old hurst]

Level Gearcase. Fill from bottom to top vent plug.

Raise trim for 2 minutes, rotate propshaft.

Level gearcase. Fill from bottom to top vent plug.

Repeat above until the level is AT the vent opening when you come back to LEVEL.


(The key here is that you're ensuring that gear lube is migrating all the way up into the forward cavity of the gearcase, resulting in the correct LEVEL when the gearcase is LEVEL).

Thanks Don. I lost a lower shortly after my 20hr service and it was definitely low low so I'm going to do it myself. Thanks again!

[Welaka]

Good info, Id bet most are low a few ounces after reading this.

[ifishinxs]

Sorry to bring this back to the top. I think this should be a sticky.

I just did my lower unit oil change on my 175. I did the normal fill until the oil comes out with some air bubbles. Then I remembered this thread.
I tilled the motor up for a few minutes. Lowered the motor back down and no oil came out. It took a few more ounces before oil started coming out the top hole. This time with no bubbles. This is the way!

[EuropeanAM]

Sorry to bring this back to the top. I think this should be a sticky.

I just did my lower unit oil change on my 175. I did the normal fill until the oil comes out with some air bubbles. Then I remembered this thread.
I tilled the motor up for a few minutes. Lowered the motor back down and no oil came out. It took a few more ounces before oil started coming out the top hole. This time with no bubbles. This is the way!

Different gearcase but still pertinent. Just make sure you're filling JUST TO THE BOTTOM of the vent opening (not spewing out, so there's no way to be seeing "bubbles" unless it's spewing out the opening).

[Pulsare2020]

Different gearcase but still pertinent. Just make sure you're filling JUST TO THE BOTTOM of the vent opening (not spewing out, so there's no way to be seeing "bubbles" unless it's spewing out the opening).

Don, I assume filling it to the bottom of the vent opening will still provide sufficient volume for gear oil expansion due to heat without stressing the seals?

[fly by night]

No worries if that is what Don suggested you do!

[EuropeanAM]

Don, I assume filling it to the bottom of the vent opening will still provide sufficient volume for gear oil expansion due to heat without stressing the seals?

Absolutely. There is a SIGNIFICANT amount of room for expansion (these cases are literally run with level near the centerline of the propshaft).

[Jasonrs]

I just did a fresh lower lube change, and with this procedure, I got 4 oz more in the lower than I ever did before....hopefully I haven't hurt my lower by running "low" in the past. I do 25 hr max changes and it's always pristine looking when it drains