tach help

volangler1

Cadet
Joined
Mar 24, 2009
Messages
11
ive got a 1973 johnson 115hp & im trying to find the sending unit for the tach.
any idea where this might be? any help would great.

thanks
 

david_r

Lieutenant Junior Grade
Joined
Aug 11, 2008
Messages
1,118
Re: tach help

if your tach has quit suspect your rectifier......... there are instructions on how to test them in the frequently asked questions section............. your tach reads off the charging system

you cannot hook a auto tach to your ob.

you can get partial repair manuals on googlebooks.com but if you are gonna be doin a lot of work on it yourself you really need a manual.
 

Texmill

Cadet
Joined
Feb 24, 2009
Messages
27
Re: tach help

Look for a grey wire in your wiring harnes. I found a grey and a black wire capped off behind the dash.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: tach help

On many of these early crossflows, there is a grey wire (tach signal) running up to the control box in the main wire harness. OMC usually cut the wire and left about 4 inches of the wire dangling loose in the box. If you open up the box you should see the wire. There should be a small hole in the underside of the control box between the two halves that is made for the wire. Pull it through that small hole and wire it to the signal pole on the tach. You will also need a positive and neg.
 
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