iv got a bravo one sterndrive, my trim goes up and down normally in neutral, and at very low speeds, but when im at wot it wont go up, but it will go down. the pump works, because i can hear it and the voltage meter shows activity. i dont know whats wrong help please

If you put the drive up when on the trailer, does it drop down at all over a few days???????

If you have done some work lately, the trim lines (and relay wires)are probably crossed. The trim out/up pressure is higher than the trim in/down on the pump, thrust load requires more pressure. Hope this helps!

Mostlikely,,,bad trimmcylinder !

does the oil in the pump look milky/foamy ????

I bet it does . Whatsoever if not ,,,reverse the lines and try again ,,,if that does not help,its the pump itself. But i doubt that.

the oil looks ok, and is if i leave it up it stays that way.... im going to try reversing the lines nex time i go to the marina, but if i do this wont i need tu purge the system?? how do i do that???

Just change them on the pump ,,,only a little oil will trip out and NO u dont need to do anything.

I still think it may be a o ring failure in the cylinder ????

is the trim switch in the throttle handle?

Unhook both trim cylinders,push on both if theres a leaking o-ring you will be able to push it in & out.

Just throwing this out there. Is your alternator charging correctly?
When mine went out once. The battery was so dead, When I hit the trim switch it actually got to the point it was cutting coil power to the engine.

Does it lose trim position while running? If not, probably not an o-ring. If the pump cannot overcome the thrust load, not enough psi from the pump.