2001 Mercury Mariner 50-60HP Factory Service Manual, Page 325Get this manual
POWER TRIM
Maximum Tilt
With the piston rod at maximum travel, and due to no rod movement, the pressure inside of the trim cylinder (w) will increase to the pressure required to move the tilt relief piston (s)The tilt relief piston's "pin" opens the tilt relief valve (r)Up pressure flows into the trim relief passage, and returns back into the reservoir