Problems with wakeplate?

I have a '05 Supra 21v with the hydraulic wakeplate. When I put it all the way down while riding, the gauge slowly creeps back up. It eventually gets back to all the way up and the needle on the gauge vibrates slightly. We just purchased this boat this winter and I don't have much experience with the wakeplate. I checked around the pump and couldn't see any fluid leaking. The fluid level is reading full as well. I haven't noticed it until the other day and the water was really rough. Could this be normal for rough conditions?

How fast were you going?

its def. not normal. i would say its probably the ram that connects to the plate. have u got in the water and checked to see what position the plate really is in. maybe its just a falty gauge and the plate is staying in the original possition.

check the lines conections!....

I haven't got in the water to check the position, but I can tell by the way the boat was riding that the plate itself was moving. I also checked it on the trailer while my wife worked the trim up and down. Everything seemed to operate normal. I had the perfect pass set for 23 but was not pulling a rider. We still haven't ridden behind our new (to us) boat! I will be glad when all our sea trials have been completed and we can go out and enjoy our boat! Is there a way to test the pistons on the plate? Can they be rebuilt? Should I just bite the bullet and take it in for service?

I had that problem once and had to replace the pump. There was a piece in the pump that was not closing and the hydralics were losing pressure, causing the wakeplate to go up.

There are 2 solenoid valves in the hydraulic power unit. More than likely one or both of them in not closing all the way causing the fluid to bleed back into the pump. Solenoid is like $50 if its a Bennett. There is a red and green valve for port and starboard. Also could be in wiring Bennett has a guide to troubleshooting on their web site