Trouble trimming down

[fishhawk5]

2015 150 4s #2B140279
Seems to trim up and down fine cold. Go run the boat 5-10 minutes and the trim doesn't want to go down even though you can hear the trim motor running. Will go down in very small increments if you keep clicking the switch. Brought home, trimmed all the way up to check the fluid level. Fluid was a little low, topped up, put the cap on, wouldn't trim down at all. Trim motor was running, just not moving. Had to lower it with the manual valve. Read alot on hear about limit calibration and modules, but wouldn't that stop the trim motor? Thanks for any help!

[EuropeanAM]

Correct. Limits are electrical- it sounds as though your problem is HYDRAULIC.

When you checked the trim fluid level, was the TRAILER (and boat) LEVEL? It needs to be....

[fishhawk5]

Yes, the boat was sitting level. I've ordered a seal kit. and plan on taking the pump apart to inspect. Spent many years working on hydraulic suspension on Benz as well as automatic trans, clean clean clean! Thanks Don!

[EuropeanAM]

I would replace the check/relief valves FIRST (have seen some that just bypassed for no particular reason).

[fishhawk5]

Replaced the check valves, pressure relief valves and all seals, works perfectly.