tach not working

[bkruger]

Hey all,<br />My tach quit working on my pontoon boat. It's hooked up to a '96 50 hp Johnson. It quit working after I had the motor rebuilt, but the mechanic wouldn't do anything about it. My "new" mechanic tested it at the tach and found that I'm getting impulse signal to the tach, but he finds it odd that the tach just quit. I was wondering if there is a way to test it? I don't know the brand, but it has 4 connections on the back. One for the backlight, impulse, ground and 12v. There is also a dial on the back with the numbers 2,3,4,5,6 next to it. It is also labeled pul/rev. I notice that when you turn the key to the run position, the needle pops up to 0, but it never goes any higher once the motor starts. <br /><br />Any suggestions?<br /><br />Thanks,<br /><br />Bill

 

[OBJ]

Re: tach not working

Bill....no pun intended here....maybe the darn thing is just broke. They do go south on occasion. Know anybody that you could borrow one from and hook up? I believe the pulse setting should be set at 6.

 

[bkruger]

Re: tach not working

Hey OBJ,<br />I'm starting to think the same thing. Just odd that it worked before sending it to get rebuilt and never worked since I got it back. I've been looking online for an exact replacement. Do all marine tachs have the same connections in the back? And yes, mine is set to 6 on the dial. I guess that isn't for the number of cylinders?<br /><br />Bill

 

[rickdb1boat]

Re: tach not working

Is your charging system working? If not, you could have a blown rectifier, which would account for the tach not working. Check and make sure. When the motor is off and you check the battery with a voltmeter, you should get around 12.5 volts. When running the motor, you should see an increase in voltage, depending on how fast the motor is running.

 

[recess]

Re: tach not working

Same thing on my 1974 70hp. Tach just quit. Bought a used tach; also, no go. Was reading a post on here about the rectifier and one sentence caught my eye. "Once the rectifier is replaced, the tach should work." I tested the rectifier according to the info on here and low and behold, no good. Changed out the rectifier and the old tach was good as new. Now I had run the boat without the tach last summer, and was getting some charge to the battery, I guess through one leg of the stator. I never realized I had an electrical problem until the tach quit working. Do a search on how to test the rectifier. Its an easy fix.

 

[DJ]

Re: tach not working

If the rectifier is gone, the battery is not being recharged either.<br /><br />Easy to check, put a voltmeter across the battery terminals and run the engine. If you get over 13 volts, the rectifier is working.