1997+ Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-826148R2, Page 231Get this manual
TILT UP In the up mode, as the trim rod (b) extends from the cylinder, the memory piston (e) clears or uncovers the pressure relief passageOil from the up cavity will enter this passage and open the tilt pressure relief valve (k)This valve lowers the amount of pressure available to lift the outboard motorWith the engine in forward gear, and at high engine rpm, the oil pressure available will not be able to overcome the propeller thrust, limiting the trim range to below the pressure relief orificeWhen the engine rpm's fall or if engine is not in forward gear, the oil pressure is available to extend the trim ram (b) up into the tilt range