Having issues with my sons' boat. 1988 Startos 179V w/1986 Mercury 150 Black Max XR2 motor. Out of clear blue, started having issues with trim up. The motor will trim up and down from all switches- throttle handle, front control panel and rear stern location. But when throttling forward at about 1/3 and higher, the trim button will not raise motor (even when barely under way-minimal resistance on motor). As soon as you back throttle down a smidge, it works. Works when just "putting" in no wake area. When button is pushed to trim up, I see 12 volt meter react but motor does not move. Any insight/help is much appreciated.