Tilt and trim guage 1989 Merc 75 hp Wiring and signal

appleo

Petty Officer 1st Class
Joined
Jul 19, 2012
Messages
380
Picked up a used 75 hp

1. any clue where the tilt trim position rocker switch is located
2. How many wires?
3. How to connect wires to the trim dashpanel gauge?
4. Are tilt trim gauges universal? Evinrude swapout for a Mercury gauge?

any tips appreciated winter here in syracuse boat is tarped for the winter
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
23,840
Well, it doesn't look like Mercury made a 75HP motor in 1989. It is either 70HP or 80HP.

They do show a trim sender for the 70HP motor. It is on the transom clamp. It should be 2 wires, ground and sender. The sender wire would connect to the gauge.

Not sure if the J/E gauge will swap with Merc. Doesn't hurt to try it, if you have the gauge.

Not sure if your wiring harness already has a wire for trim sender.. If not you will need to pull one.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
13,623
Chris,
I just picked up a 2002 115 2 stroker with a trim position sensor. Do you know how the signal is generated and what changes the reading?

I assume there is a Rheostat with the movable arm connected to the engine and the rest connected to the clamp bracket. Changing resistance changes the current and thus the position of the needle in the dash monitor. In asking the question I am curious as to calibration. Since different boats have different transom angles, if one wants a certain mark on the meter to represent a desired trim position it would be nice to calibrate it.

Also, just a side note of interest is how is that made waterproof considering the tilt range of the engine to clamp bracket interface.

Thanks.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
23,840
You are correct, the trim sender is a variable rheostat. The movable arm is likely sealed with an oring, although, I have never taken one apart.

There is probably no calibration. That would require an adjustment of the position (relative to vertical) of the sender.

You will likely find that the trim gauge is not real reliable and therefore not real useful. It is always best to trim the motor by sound and feel of the steering, as well and how she handles.
 
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