Tachometer problem... 115 HP Evinrude (1978)

[Guvner..]

I bought another tachometer. This one had a terminal for Evinrude/Johnson motors but I didn't fare much better. I went with what was there originally which was the power switch sends the 12 volts to the IGN. terminal. Ground goes to GRD and I used the EVN/JHN terminal that was an extra on the Teleflex in addition to the normal SEND that I left unhooked. <br /><br />I get a tiny reaction to turning the 12 Volt on. Just a shake of the needle. Motor doesn't make the RPM's do anything. Sits on zero. Traced the wire back to the terminal block that I've got going to the EVN/JHN terminal. That was the wire that went to the sender on the original 2 wire tachometer. I did a continuity test and the wire ohmed out to the terminal. I think it is the 4th one down from the top. I believe it is still Gray when it gets there. (Thicker than it was.) What should I get for voltage there if I just hook a meter between ground and the gray wire going to the terminal? I think I was told to put it on AC instead of DC. <br /><br />Any help would be appreciated...<br /><br />Thanks... Gary

 

[Skyhigh]

Re: Tachometer problem... 115 HP Evinrude (1978)

Does your control box have the 3 wires coming out of it?<br /><br /> b<br />a c<br /><br />On the one i have B is pulse, check in ac mode should go up when engine goes up.<br /><br />C = Ground (Black)<br />B = Pulse (gray)<br />A = was 12v DC (purple)

 

[Guvner..]

Re: Tachometer problem... 115 HP Evinrude (1978)

My gray wire doesn't come up much on an AC meter. 3 volts maybe... I need to get an idea of what it should read just checking at the engine between I presume a ground and the gray wire. <br /><br />Any ideas of what it should be at idle?<br /><br />Thanks... Gary

 

[Guvner..]

Re: Tachometer problem... 115 HP Evinrude (1978)

According to Teleflex the gray wire should be 3 to 5 volts AC current at idle. Mine has that until you hook it to the tach. Under that little load it goes down to 1 volt or so... I guess I need a new rectifier from what I'm gathering from all this... <br /><br />Any other comments?<br /><br />Thanks... Gary

 

[rickdb1boat]

Re: Tachometer problem... 115 HP Evinrude (1978)

Guvner<br /><br />I wouldn't put another rectifier on until I tried still another Tach. Check out the charging system to be sure. Ya never know if the new tach is defective. Once the gray wire is under a load, the volts will show a drop, even if the tach is not registering properly.

 

[Guvner..]

Re: Tachometer problem... 115 HP Evinrude (1978)

I've had two tachs on it now but I'm not sure the one that got dented in the mail should count. I did notice that the terminal just above the gray and gray/yellow wires did read out 20 volts or so on AC but not sure what part of the circuit that is. I did read the battery voltage while the engine was running and had 12.88 volts. Not sure what it should be at an idle. <br /><br />Thanks... Gary

 

[rickdb1boat]

Re: Tachometer problem... 115 HP Evinrude (1978)

Gary<br /><br />Using a volt meter, check the battery voltage with your engine turned off. It should read somewhere around 12 - 12.5 volts. Then start your engine (be sure it's in water or has ear muffs and garden hose attached) and then read the battery voltage. If your engine is charging properly it should read around 13.8 - 14.2 volts, depending on motor speed. Sometimes it will read higher if it's an unregulated charging system or the battery is defective.<br /><br /> Check this out:web page