Johnson tach

[chads]

I have a 1975 Johnson stinger 2 75hp. I replaced the tach with a Sierra 3" Arctic tac. The original never worked since I bought the boat. After installing the new one it also does not work. I stare ted doing some trouble shooting. The gray wire from the control box is attached to the send side of the tach. I assumed there must be something wrong on the engine side. With the rngine running I have approx 62 vac at the gray wire coming from the control box. With that wire hooked to the tach I have approx 32 vac voltage drop between the send snd ground post on the tach. I also have about 13.2 vdc at the battery with the rngine at idle. Does this all sound like I have a bad new tach? The lights work, it drops to zero when batteries are turned on, the needle just never moves while hooked up with the engine running.

 

[emdsapmgr]

The engine has a rectifier assembly connected between the battery and the some of the coils from the stator. It's to charge the battery. The rectifier also creates a pulse-signal to drive any marine tach. The tach runs off these pulse signals, not off spark plug flashes. Possible your rectifier is not working. Do you know if the engine is re-charging the battery or not? If the rectifier is shot, your tach won't work.

 

[chads]

Yes the engine is charging the battery at about 13.5 volts. I can measure about 64vac at the gray wire from the control box. At the tach I can measure a voltage drop of about 33vac between the send post and ground. Sea star is sending me s new tach, hope that fixes the problem. I want to get the tach working, get the impeller changed and perform the service bulletin for the pee line. All this before June 3rd, I promised a father/dayghter say on the boat.

 

[chads]

Forgot to say that the vac readings were at idle

 

[oldboat1]

If running into time constraints, might help to know that the SB referenced newer motors -- wouldn't consider it real urgent (imo).

 

[chads]

Ok now I'm lost and need help. I put a new tach on the engine, still no good. so I did the following:

1- unhooked the rectifier from the terminal strip
2- read about 20vac at the stator wires at idle
3- ran jumper wire from yellow/gray stator wire to tach sig terminal. Worked one time then quit. Have not been able to get it working again
4- read about half vac between tach ground and sig post with engine at idle.

What am I missing. I am at a complete loss.

 

[emdsapmgr]

Is your arctic tach considered a "Marine" tach?

 

[chads]

Yup, it's a marine tach

http://m.overtons.com/modperl/product/details.cgi?i=73293

 

[Faztbullet]

You have a rectifier problem as you should only see about 5 volt AC at idle not 60 VAC

 

[David Young]

Thank goodness the rectifier is one of the cheapest replacement parts we have on our boat motors

 

[oldboat1]

think unhooking the rectifier while running might have burned it out.

 

[flyingscott]

YUP

 

[chads]

Well, after all the trouble shooting I finally broke down and ordered a rectifier as a last ditch fix. I can't explain how but that's what the issue was. Battery is now charging correctly and the tach is working.