Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 288Get this manual
Motor and Electrical Tests Trim Pump Motor Test
AWARNING
DO NOT perform this test near flammables (or explosives)as spark may occur when making connectionsRemove pump from boat, If necessarybefore perfo rming test1Disconnect blue-wh ite (motor) wire from term inal onUp" solenoid