Power tilt sticks in the up position?

[foreveryoung]

I have a yamaha 1998 250 hp saltwater series OX66 and after I leave it in the full up position for a few weeks it wants to stick there. I have to repeatedly go up and down with the trim switch till I finally get it all the way down. Once its down it works fine its just after it sits for prolonged periods it wants to stick. I can hear the motor loading up when I first try to make it go down then I pause go up then back down till it loads again and repeat till I'm all the way down. Any ideas? Thank you.

[boats.net]

Could be one of the Sub Valve's, number 54 Yamaha Outboard Parts 1998 S250TXRW POWER TRIM & TILT ASSEMBLY 1 Diagram
or one of the relief valves inside unit.

[jb123]

could also be tilt tube seizing up, pull top pin on tilt and see if motor lifts freely by hand.

[Brisco58]

I have a 1998 150 VMAX that was having the same issue last year. I had to use the manual release several times in waist deep water after fishing a shallow flat and drifting into deeper water. I ended up changing the fluid in the assembly, bleed the system thoroughly and applied a generous amount of grease to the rams and the seals around them. I have not had the problem since. I also cleaned the rams thoroughly and checked for burrs and other imperfections.