My 1984 Evinrude 150Hp tilt stopped working. It won't move either direction. Back story:
Went to winterize boat. Raised the outboard, later it was stuck in full up position. Lowered by Manual Release Valve. Fluid looked very "frothy". After checking fluid level and topping it off, fully charged battery, trim motor sounds fine in both directions.....It won't move in either direction.

I have since removed the pin, connecting it to the outboard, still no movement in either direction. I can release the MRV and move the tilt cylinder. As a side note I pushed the tilt cylinder all the way down, tightened the MRV closed. When I attempt to cycle the tilt system in the down position the tilt cylinder slowly creeps upwards??

I have seen where ppl say they "rebuilt" the system but only mention seals, o-rings etc. Is it not common to replace everything inside (assorted check valves etc)?

Also, as I was researching seals and o-ring kits I can not determine what type of tilt cylinder I have. I have looked for any type of numbers located on the tilt cylinder with no avail. I know it is supposed to have a P for Prestolite or S for Showa after the number

sounds like its hydraulicly locked up/ it does happen to those units if not trailered correctly. there is a trick to repairing it that you can do. remove the valve that is located at the bottom left side of the unit but first put the engine on the tilt lock on the engine after you remove the valve put a 1/4 x 20 nut in the housing flat with the vale in the bottom of the opening and reinstall the balve that you removed. that will relieve the pressure on the valve. remove valve and the nut and reinstall the valve you may lose some fluid soo you may need to top off when finished

i'll take a look at it tonight. thanks.

Over due update. I replaced orings and seals in trim and tilt. The scraper seals were complete toast. Took a minute to get it bled. After multiple cycles there was still lots of air that wouldn't bleed. I loosened the manual release valveand was able to get the rest of the air out. Works like a champ.

glad you got it going and thanks for the update!