i have a merc 170 i/o the trim is stuck in the fully up position, bypassing the limit switch i hear the pump whirring when the down button is pressed, when the up button is pressed just a click. its an older pump with the solid metal reservoir. i disconnected the 2 lines rummin to the pump , the down buttom produces a stream of flid out one of the holes , however the trims down go down, any tips to help me test if its the pump or the lines or the trim arms ? i woudl hate to replace it all when only 1 part is bad,