You can't overfill the drive. When you put oil in the resevoir, it fills in the air space in the drive. The level will drop some the first time you run as the remaining air bleeds out. There should be no air left in the drive. This is how it is designed to operate. If the oil level contimues to drop after every time you go out, then you have a leak.

Hmmm. . . if this is true then if you overfill the resevoir up to the cap and the fluid tries to expand when the oil heats up, it Would raise the pressure!

We are NOT over filling the drive. The resevoir is over filling the drive. We start out with the right amount of oil, then after a short run the resivoir goes down, and the drive ends up with too much oil.

Can you explain to us how a drive can have 'too much' oil please???

The drive is not completely filled with oil.

It's to be filled to the level plug on the side
of the upper.

The oil in the reservior is there to maintain this level
if fluid loss occurs.

There is a check valve in the reservior cap.

That is normal. When you change lube, you only use the upper plug to let the air out as you fill. After a little use, the reservoir goes down and fill the the drive to the top, beyond the height of the upper plug. After a lube change, mine would use about half the res bottle in the first trip out.

I would say you are either getting too hot or the seal was just weak.

The reservoir CANNOT overfill the drive. The drive is meant to be filled beyond the top plug. You have a pressure problem that is most likely being caused by too much heat. If its not a heat problem, then its just a bad seal.

I do remeber reading threads about the upper seal having problems and being redesigned.

For what its worth, here's how we fill the drives:

With upper plug removed, fill until it runs out of
upper plug.

Put in upper plug.

Continue to fill from bottom until about an inch
of oil is in the bottle.

Put in lower plug.

Top off bottle.

That's the procedure from the Merc manual anyway.

Pesky Varmint

Like said above you can't overfill the drive on a bravo. If my bad memory is correct than so is Pesky Varmit on the correct way to fill the drive.

That's how I do it.

The initial loss of fluid after the first run is usually
due to the drive "burping" up some air that may have been
pumped in during the filling process, or an air pocket ,somewhere below the reservior fitting in the drive, releasing.

I usually overfill the reservior slightly, so after it burps,
it's down to the normal line.


I had a seal failure once, and it was due to a nick
on the input shaft yoke.