One difference between oil and water in a hydraulic system is the oil WON'T turn to air when a vacuame is put on it. ( raising the drive by hand will cause a partial vacuame on the cylinder) Drain the oil/water mix from the reservoir and the cylinders and refill.
To get the air out of the system remove the rear bolt and let the cylinders hang down. ( make sure they don't rub on anything.) Then run the trim in and out about 100 times. Make sure you bottom the rams in both directions.

If you fill the cylinders properly, as I discussed earlier, you can avoid getting much air at all in the system. Engine oil does airate and foam easy. The pump is bi-directional and uses the returned air/oil before pulling more oil from the reservoir. It wouldnt' bleed out the air at all except that the cylinder volume is different on the extend vs retract which forces some returned air/oil into the reservoir when retracting. Then it needs more oil than what is returned on extension, pulling oil in from the reservoir, this does help slowly bleed air out of the system, but once the oil is foamed up, it takes a while to separate.
It is fairly simple to just attach the hose that will fill the cylinder with it at one end of the stroke, don't attach the other, it will just push air back into the pump. Sealing the open hose will prevent it from trying to pull some air into the pump. There will only be a slight amount of air that is in the hoses, unless you run the pump a little in each direction to get solid oil at the hose before connecting it. It is harder to explain and sounds a lot harder than it is in practice.

I think I have this issue licked!

[YOUTUBE]http://www.youtube.com/watch?v=XALql86_VaA[/YOUTUBE]

Much better now!

Looks real good! What did you all find?