My Stbd. drive is giving me problems.
The trim acts normally when on the lift, up-down OK.
However, when out on the water, under power, it won't pick the drive up.
I have replaced the trim pump with a new one and now don't know where to look.
Could it be some bad wiring and the amps it is drawing when under load are too much?

Help please.....

Switch the hoses around at the pump & try again.

I am not sure I understand.
Is there a high pressure hose that I am missing?
The drive does go up and down, when sitting still.
It is just under load, it won't go up, but it will trim down while under power. If I trim it partially, hten get on plane, the drive holds it's position.

We're having the same problem on a Fountain. Checked voltage to the pumps and all is good. Any thing else to check out?

Just a thought. May be one of the o-rings in your trim cylinders is damaged causing the fluid to bypass when under pressure and weight of the boat.