Trim Gauge changes with engine speed

[ldbruce]

I have a 1982 Mark Twain 17.5 ft. ski boat with Mercruiser I/O drive, 228 HP. I have replaced the trim sender unit twice with new ones. The sending unit and gauge work perfect with key on, motor off, throughout the entire trim range. When engine is started, trim gauge needle rises and fluctuates with engine RPM. Seems like varying voltage from the alternator is causing gauge to vary. Anyone have any ideas? Thanks in advance.

 

[tommays]

Re: Trim Gauge changes with engine speed

I would unplug the round plug between the motor and boat ,clean it out and put it back toghter


All the control power passes through and it gets a bit nasty in the pins and makes the guages do flakey things



Tommays