Trim works good up and down when boat is on trailer or in water. But when it is on plan it will not go up. Trim pump runs but will not go up. Any suggestions would be great.

Cylinder orings bad. Do not have enough seal in the cylinders to over come the pressure of the engine pushing the boat. Guess?

Check and make sure the hoses are not reversed. I had same problem on a boat I bought from some dope. He had switched them when he put in new pump.

The hoses on the trim pump or the rams?

My guess also. Or could be low on fluid.

Thanks,Guys went out to day changed the hoses and wires going to the trim switch and it works fine.That is why the guy I got the boat from said it only went 85mph He must of not felt the bow digging in to the water.

Lol I had same stupid problem Took me weeks to figure it out After I rebuilt trim cylinders and replaced the pump.

Up north they always need longer Mike !!!!! LOL