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VetteLT193
02-07-2009, 09:35 AM
My merc trim pump is not working right, obvious wiring issue... I haven't gotten to it yet, but I need to get the drive in trailer position to move it.

I hot wired the power cable and I have a good ground (tested)
I jimmy'ed the trim switch up and by messing with the wires the drive went up some... but then stopped. At least I know the pump is ok.

What is the fastest / easiest way to hot wire the trim pump to get the drive up?

There is a 3 wire plug in harness that looks promising, but which one is trim stop limited and which one is the trailer?

BUIZILLA
02-07-2009, 09:42 AM
you have two solenoids at the pump...

one is for trim and the other is for tilt....

if you have hot 12v at each solenoid, jump the large lug with the accordingly active small lug

DonziJon
02-07-2009, 09:49 AM
Pull the cross bolt at the aft end of the rams? Raise drive. John

VetteLT193
02-07-2009, 09:54 AM
you have two solenoids at the pump...

one is for trim and the other is for tilt....

if you have hot 12v at each solenoid, jump the large lug with the accordingly active small lug

hmmm, I'm not seeing that or I'm looking at the wrong thing. I see a plug harness with 3 wires, the wires correspond to the wires in the shifter trim switch (I think). Those three wires are bundled in with a couple more that look to go back to the trim limit


Pull the cross bolt at the aft end of the rams? Raise drive. John

I might do this...

VetteLT193
02-07-2009, 10:03 AM
I got it after staring at it for a few minutes...

Pulled the wiring harness / plug with the three wires going into it.
took a test wire, put one end of it into the 'red' prong (right hand side)
touched the other end of the wire to the top prong (drive went down)
touched the other end of the wire to the lower prong (drive went up)

I think mine is wired so that the trim stop kills the loop, so the wires run from through the trim stop to the throttle handle then daisy chained into the trailer button. The trailer button is outside of the trim stop loop.

thanks for everyone's help!!

BUIZILLA
02-07-2009, 10:07 AM
The trailer button is outside of the trim stop loop. that's what the second solenoid is for...

DonziJon
02-07-2009, 10:17 AM
If you suspect the Trim Stop limit switch (left side of the drive) is the problem, here is a procedure for fooling the system, allowing you to raise and lower the drive from the throttle as designed.
________________________

Could also be Rotten Wiring running from the Trim Limit Switch on the left side of the drive through the transom. In older boats..say mid-late eighties, water (particularly salt water) wicks up into the wire and actually rots the copper core in the wire running from the Limit Switch ("Hockey Puck") through the transom.

When this happens the trim circuit "Thinks" the drive is full up and will not lift the drive when you use the throttle trim switch. You may however be able to lift the drive with the trailer switch... this doesn't work well while under load however.

This wire is a PITA to replace. However, you can "Fool" the circuit. Go inside the engine room on the port side down near the oil filter (350) and unwrap the wiring harness to expose all the wires. Reach aft along the harness and find three single wire conductors bundled together. TWO of the conductors will run into a Single PLUG.. the other conductor will go into another plug. These 2+1 conductors will plug into TWO inline plugs that lead to the transom assembly where they exit the boat to the drive.

PULL (disconnect) the plugs from the two conductors going out through the transom ass'y. NOW: take the 2+1 conductors and "snip" the plugs OFF. You want to twist all three wires together. We are talking about the wiring Harness side. Forget the two wires exiting the transom..they are junk. (The TWO Harness wires together are BOTH Blue/White. The single wire is Purple/White.)

NOW try the trim switch on the throttle to see if the drive lifts up. If it does, your good to go.

WARNING: You have now fooled the circuit into thinking that the drive is NOT Yet FULLY UP.... so NOW.. when you lift the drive with the trim switch on the throttle, the LIMIT Switch (hockey puck)
is inoperative and you MUST actually WATCH the drive as you lift it.. OR you can Jam the drive up into the Gimbal Ring.

This whole thing is a little inconvenient to live with but you can learn. I have been using this for over three years without a problem. Just keep an eye on the drive when you want to lift it up FULLY for trailering. None of this affects the trim GUAGE on the dash. It will still work normally. It's just not as accurate as your eyeball. John

BigGrizzly
02-07-2009, 11:00 AM
Just a though, if you have the 3 button trim you hold the top and middle buttons down at the same and that jumps the trim Limit switch hocky puck.