tachometer problem

[ken s]

Hi all,  I'm new to the site and have a problem with my 17.5 Aquasport tach.  Two years ago I brought it to an idiot to have it winterized and have the fuel gauge replaced.  they left it out, apart, and open to the rain for two months. Never got the gauge...
    When I started it the following spring, the tack will not work.  the lights on the gauge that check the motor, (a 90 HP Johnson) work fine.  but the tach is dead. everything worked fine before the 'service',  
    Any ideas???  Thanks  Ken  

    Coast Guard Facility boat, Chatham MA.  Flotilla 11-1

[GoneFission]

Check the wiring connections on the back of the tach - a wire might have become loose or unplugged.  After that, the next step is to follow the wire back to the motor and make sure it's not broken or disconnected somewhere along the way.  Good luck!

[200CCPMerc200]

I dunno about jonsons, but, most tachs will have a 12 volt "ignition" lead coming in from the key harness on the control box, then another wire in that bundle that connects to the "signal" pole on the tach, then your ground. You also must set the dial on the tach to correspond with the # of cyls. On your motor. Sometimes, you just need to move that dial a bit and reset it, as they get dirty.

[seabob4]

As has been said, it could be a number of things.  But I would definitely check the gray wire on the back side of the tach, that is your tach sender lead.  Purple is ignition power but you definitely are good there as that also enables the System Check function.  The gray wire will have what we call "sense voltage" on it if all is good, somewhere in the range of 5.5V+...

[200CCPMerc200]

Bob, are all motors the same wiring colors ? I didnt wanna' confuse him with purple/gray as i thought only mercury used that.

[seabob4]

Bob, are all motors the same wiring colors ? I didnt wanna' confuse him with purple/gray as i thought only mercury used that.

Chris,
Not ALL the same (think Yamaha, Honda, Zuke), but in Merc and OMCs, yes, purple is ignition power (switched), gray is tach sender.  Brown w/white stripe is trim sender on Mercs, OMC uses white w/brown stripe...