Analog tach hookup for merc 25 2s?

Discussion in 'Outboard Maintenance' started by Dillusion, Nov 30, 2012.

  1. Dillusion

    Dillusion devilray snob

    Is there an easy way to hookup an analog tach gauge to a merc 25 2s tiller?

    I know there is a tach harness on the engine....this guy did it with an older merc:

    I have a it doable?

    Looks like it's the same hookup and the same wires on my 04, will report back if it works.
  2. HaMm3r

    HaMm3r Well-Known Member

    Hey Matty, yeah that was me in the link you referenced. :cool:

    In my case, I didn't have a built-in tach connection on my control box, so I had to figure out another way. 6 months later and the MSD pickup is still working great, btw. :)

    If you have a tach harness on yours, you may just be able to plug in and go. Check the specs on your control box and see if it includes a tach signal output.

  3. Dillusion

    Dillusion devilray snob

    My merc does have a "tach module harness" but I have no idea how to hook up to it.

    Ay ideas? Wll it be easier? Not necessarily easier as your fix was easier but...more native?
  4. HaMm3r

    HaMm3r Well-Known Member

    I haven't tried to look it up, but I'm sure the wiring diagram for the harness is available somewhere on the web. The tach itself really only requires one wire from the engine, which carries the tach signal. It's usually gray on Mercs. The tach will also need a positive power and ground connection, but that doesn't necessarily have to come from the engine/harness.

    I might be wrong about this, but I think the wiring harness is mostly designed to to connect to the wiring harness from a remote control box, and the tach plugs into that. Since yours is tiller, it might be easier to wire the tach in direct and not worry about the other connections in the harness.