Tach Question

dblanton

Petty Officer 2nd Class
Joined
Sep 22, 2006
Messages
101
I have a 1981 Evinrude 75hp. When I turn the ignition key to the on position sometimes the needle on the tachometer will move slightly and sometimes the needle will not move. When the needle does move, each subsequent time I turn the key to the on position the needle will move slightly, after I leave the key in the off position for an hour or so and I turn the key to the on position again the needle on the tach will not move. If I quickly bump the engine with the starter and turn the key to the off position the needle will move slightly when turning the key back to the on position.
I have set the key to the on position and the needle not move, then turn the engine slowly by hand and the needle will move slightly. I have checked all of the wiring connections and they good.
The tach does function when the engine is running.
The last time I had the boat out there were a couple of times the engine would not crank, no clicking sound, nothing, it was just like the battery was disconnected. After several times of turning the key to the start position and back off and back to start it would finally crank and start. I checked the neutral safety switch and it is good.
I thought that the ignition switch was bad so I replaced it with a new one and it cranks over every time now but I still have the same issue with the tach needle sometimes slightly moving and sometimes not when turning the key to the on position.
The engine is keeping the cranking battery charged.
Is the fact that sometimes the tach needle moves and sometimes it doesn?t move when the key is turned to the on position indicate a problem that I need to repair?
I know that my explanation of the issue is long but I wanted to give as much detailed information as I could.
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: Tach Question

If tachometer does not 'zero' when power is turned on, the POSITIVE (IGN) and/or ground wires are not connected properly. The tach must 'zero' when powered. When measured with a volt/ohmmeter, the power (IGN) to ground (GND) voltage must be 12-16 volts DC with the ignition on.
 

dblanton

Petty Officer 2nd Class
Joined
Sep 22, 2006
Messages
101
Re: Tach Question

I am assuming that this reading is at the ignition switch is that correct?
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: Tach Question

On the back of the tach...sounds more like a ground or IGN connection though, I would start there.
 
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