Need some help with tachometer - 1988 V204 - 5.0 Merc Alpha 1

CC61821

Hello everyone!  New to this group at the suggestion of Rinker customer support.  I have recently acquired a 1988 Rinker V204 deck boat with a 5.0L Mercruiser Alpha 1.  The problem is that the tachometer does not work.  I have posted in numerous forums, and even contacted Rinker support, but to no avail, so I am hoping that someone here can help me.  When I bought the boat, the stock tach was completely locked up and did not work.  I was able to replace it with another matching Medallion tach, and hooked everything back up, but this one doesn't work either!  The gauge itself appears to be free, as the needle moves when I rotate the gauge itself by hand.  I do have good power and ground to the gauge as it lights up when I turn on the nav lights - but yet it will not read any RPM's whatsoever.  I have run a new wire from what I believe to be the negative side of the coil, and nothing.  So, with all that said - where does the tach signal originate on this motor?  Should I even be trying to pull the signal off of the coil, or should it come off of the distributor?  I do not see any connections on the outside of the distributor itself, so am at a loss.  Any suggestions?  I have bought a stainless prop to replace my presumably stock aluminum one, but don't want to do so until I know what the engine is turning now. 

212rowboat

Run a direct wire from your tachometer to the engine... Don't worry about fishing it, just let it lay on the deck and over seats and such... You're looking for the purple and white lead off your ignition module... Tap into it and into the tech, with the other lead well grounded.   See what happens.  

I'd reckon wires and shields have corroded on that older rig, and you're losing precious continuity.  

CC61821

Thank you - I was thinking the same thing about the older wiring.  I too had thought about just straight-running wiring over the seats to the engine as well - I need to locate the ignition module so that I can hook into that.  Since I do not see any leads off of the distributor and hooking up to the negative on the coil didn't do it, that has to be the next step.