I've been working on this problem for the last few weeks and now I am down to either the solenoids being bad or it's the trim motor. I have already ruled out a batter problem.

Mercury 1990 2-stroke 135 hp V6

Testing
I went through voltage testing per the service manuals flowcharts.

Essentially all tests seemed to point to checking ground contacts (I've done this), testing solenoids, and testing the motor itself with an indication that the motor might be bad.

Interesting tid-bits
I took some sand paper and cleaned up all of the contact points but this didn't resolve the problem.

What I had noticed that seemed interesting was the following:
1) When testing the UP solenoid, it checked out for voltage when pressing the UP button. When pressing the DOWN button the UP solenoid also showed a full voltage reading. I should note that this test was testing the wire leading to the pump (i.e. blue for up, green for down), not the power lead (i.e. red). So in this test case, both solenoids had a voltage reading when either button was pressed.
2) Vice versa for down solenoid
3) In the Service manual when testing the solenoids:


Continuity for me read .5 after calibrating my tester; this reading was close to 0 but not quite.

Questions
1) Should it make sense that when the down button is pressed that the up reads a voltage and vice versa? With my novice understanding of electronics, this doesn't seem right.

2) Is close to 0 reading for resistance good enough or does the fact that my tester did not read 0 on the solenoids indicate a problem? Being just a simple diy-er, I can't say if the resistance test has to be exact or not.

 

I guess I never really outlined what my problem is.

Whenever I press the up or down on the trim, the respective trim solenoid makes a single click sound; however the trim motor does not react.

 

Most likely you have a bad motor. A quick easy test is to power the motor directly and see if it moves. if it's a two wire motor touch the blue wire to pos and green to neg and it should move up on a three wire blue to pos and black to ground. It should go up if not you have a bad motor. If it does move you have a power or ground problem.

 

Yep.

Three wire motor, took jumper cables red to blue, black to black - I seen a spark and the motor turned for a 1/4 second. Tried multiple times after that, red to green and black to black with nothing. Motor didn't turn at all and I didn't get a spark.


How does one get the trim motor removed for service? I've been reviewing my engines service manual on the steps and it involves removing the left transom while holding the starboard side engine with a block of wood and a c-clamp All the while I am to remove the trim pistons from the engine.

it looks like just regular tools can be used though...

 

I'm not sure if I would trust a c-clamp and wood to hold it up while I'm under it. I lift the motor by the flywheel and remove the port clamp bracket.