Checking Tachometer

[fmjnax]

When I bought the boat, it had a tachometer installed, but all the wires cut (from when the PO replaced motors is my guess). I decided to hook it back up so I ran a splice from the gray wire in the control box, an ignition wire, and a ground wire to the tach. However, it doesn't work. The light works, but that's it. The setting dial on the back does not have numbers on it so I have no idea what the pole setting is as I turn it. With the motor running, I tried to turn it until it worked, but the best I could get was an intermittent needle jump.

Is there a way to test the signal wire that I ran (or the tachometer itself) to make sure it's not loose or broken before I dig into it any further? My charging system works flawlessly so the problem is either in my wiring or in the tachometer unit. I just don't know how to tell which.

 

[F_R]

In other words, you have no clue what system the tach is designed to work on. You appear to be trying to use it on an alternator system, but there many older tachs designed for battery ignition, magneto ignition, or electronic ignition. Those are somewhat valuable because they are no longer made, so if you can ID it, find a proper home for it and buy a new alternator tach here at iboats.

 

[fmjnax]

I guess that could be another spin F_R. I know the original motor was a Suzuki, probably an '89 (since the hull is also an '89) in the 115-150hp range. Of course, that probably doesn't help any. I didn't even think that maybe it was a completely different system. The motor that is on there now is an '84 Johnson V4 115hp.

 

[F_R]

While I know nothing about Suzukis, I would assume that would be an alternator tach and should work on your Johnson, even though the RPM may be incorrect if the poles count are different. But as I said, I really don't know about Suzukis..

 

[emdsapmgr]

Agree with FR. Johnson used Suzuki 4 stroke engines for years (2003-2006) painted them white and put Johnson decals on them. I'd think a marine tach from a modern Suzuki would also work on a crossflow V4. Possible the Johnson combination rectifier/regulator that's on your 84 engine may not be outputting any signal. (if so, it's probably also not charging the battery.)

 

[fmjnax]

Wow, I didn't know that emdsapmgr! I just assumed it was a Suzuki because there is a Suzuki oil guage, a Suzuki trim gauge, and the wire harness has Suzuki on it.

The charging system is working correctly. I'm getting 14V back to the battery while running and I monitor the voltage via a couple sonar units. That said, I haven't specifically checked the reg/rect, so maybe I should. First, I am going to try and clean up the wire and connections. After looking at it last night, it might be that I'm not getting a solid connection. I can sometimes wiggle it around and get it to read for a little bit (though I think it's wrong), and then back to nothing.