Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 187Get this manual
3Actuate the "Trailer" switch and trim engine to full up position4Remove fill screw (a) and check oil level in pumpOil level should be to the bottom of the fill hole threads (b)If necessary, add SAE 10W-30 or 10W-40 motor oilDO NOT overfillNOTE: In tropical areas, single viscosity SAE 30W motor oil may be used 5Reinstall and tighten fill screwVent screw stays open to vent the pump reservoir Bleeding Air from System
1To determine if the Power Trim System contains air, activate "Up" circuit and trim engine to the trim limit position Pull up on lower unitIf pistons retract into trim cylinders more than 18 in(3.2mm), it will be necessary to bleed air from the Power Trim System2Open pump vent screw (a) turns3Turn manual release valve (b) full left (counterclockwise) 4Bleed air from system by trimming engine several times thru entire trailering range Recheck pump oil level each time engine is trimmed up and add oil if necessary(