ISO Mercury/Starcraft 4 pin tach info

[Deepcover]

I have a 2005 starcraft pontoon with a 75 Mercury four stroke and the tach does not work. I have good 12v, ground, and engine signal, so I am quite sure the gauge itself is bad. My problem is that the tach has a 4 pin socket on the back and the plug from the harness is very short and tightly interwoven with the rest of the dash wiring, making it nearly impossible to splice into. The tach is a faria, but label is unreadable. Is this plug Mercury or starcraft proprietary, or has anyone heard of an adapter plug or pigtail to match up with a standard 3 post tach? The only ones I have found are the replacement harnesses for the boat, which doesn't help me. Any help is appreciated!

 

[04fxdwgi25]

If you can't find a direct replacement, then alternitive would be and aftermarket setup. But you may need to "massage the harness" but cutting into it. Below would be the pinouts

However, there is a replacement harness available to bypass what is there and provide the tach wiring for a generic marine tach.
Here is a video of installing it:

Here is the harness: https://leadersrpmshop.com/mercury-marine-new-oem-tachometer-4-pin-wiring-harness-84-69108a5/

I would venture to think that the 4 wires are:
Send - Sender (Tach signal)
IGN - Bat+ power from ignition switch
GRD - Ground (Bat neg)
LT - Lighting

This picture is from Telflex troubleshooting guide