Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 327Get this manual
POWER TRIM
Bleeding Power Trim Unit
1Secure power trim unit in soft jawed vise2Add power trim fluid until it's even with the bottom of the fill holeReinstall plug3Close the manual release valve(Turn full clockwise)
aReservoi PlugFill HoleManual Release Valve 4Using 12 volt power supply, connect the positive lead to (blue) trim motor wire and negative lead to (green) trim motor wire and drive shock rod to the up positionRepeat three times5Connect the positive lead to the (green) trim motor wi re, and the negative lead to the (blue) trim motor wire and drive the shock rod to the down position6Recheck fluid level, add fluid if required and repeat cycle until fluid level stays even with the bottom of the fill hole