I have a 1990 33Ft scarab w/ twin 454 mercruisers the boat works well but when I go to plan ,the port drive lifts up if I give it full power it rooster tails .Both drives tilt up/down well the port drive stays down when driving .I suspect a pressure leak in the keikahfer aeromarine drive pump .I don't know if I can get the pump serviced and pressure checked by itself or it could be the rams ?No obvious leaks anywhere
Thanks

Does anyone have a thought about my drive lifting up when planning , I'm still dealing with the same problem ,changed the fittings and it still lifts up
Thanks

Not sure but sounds like air in the lines.

seems like the thrust of the prop pushing forward would push it to the transom / fighting against it lifting up

agreed,, if you took all the fluid out of it the thrust of the prop would push it down until you lifted on the throttle then the force of water would lift it up. do you have a trim switch on the throttle? may be that there is a short and when you push the throttle it activates the pump?

Did that drive just start doing this or have you recently changed the fluid or made other changes? Will definitely have a bearing on the answer. Air in the lines will heat up under compression(forward under full power acceleration) and expand raising the drive.

I'd go with switch on throttle short if 1 drive trims under power but not at idle.
Wiring harnessess can be a big bowl of spaghetti so frayed spliced bad ground can be anywhere. disconnect power on the pump and go for a ride.
Tilting drive to full up and full down a couple times bleeds air from the system.

You could trim it down and then remove the power wire to the trim pump and then you could determine/ eliminate