How to service a tilt/trim on a 50 hp yamaha outboard. I think the fluid is low as the trim will leak back down after raising the engine.

LOW FLUID POSSIBLY AND THE PUMP DOES NOT PUMP WATER .

Hydraulic fluid is most likely low. Refill it, then work the motor up and down about four or five times. Recheck and refill reservoir. Run up and down several times until you get a smooth up and down motion. Recheck /refill. Any air in the line will work it's way out on it's own. Be sure to look for any leakage.

Most of those lift with a hydrolic piston. Seals might be going or need some more fluid.

Some grease on the end of the trim rams and see if it don't go away.

Low fluid level will cause it to fail to actuate and not go up or down, can also let it not hold position as well. Filling to proper leevel with specified lubricant is recommended. If you allow the level to go too low, the pump will pull air and could burn out.

Broken connection in the wiring harness(loose)

loosen engine mounting bolts and steering tube , trim engine up by releasing the valve on the side and tie up so not tocome down ! remove pin on the ram then remove all bolts and wires and should come out !

low fluid in unit and air in the system raise all the way up put safety lever down remove fill plug and top unit off replace fill plug then cycle up and down 3 complete cycles raise back up check fill level again you may hear air leak out when removing fill plug if low fill again repeat this cycle until unit stays full this should fix the problem if not the pressure relief valve is faulty if there is no external leaks

check the control box , use multi metre and check the trim button and ignition key ! check main harness socket on the engine for corrosion or breaks in the wires !