tach problems

[mauimike]

hey guys. I have a 1981 johnson 60 two stroke with electric start. The tach has not worked since i got it. i tried changing out the tach with no improvment. I inspected the rectifier and found the red wire completely smoked. Ichanged this out and ran the motor on muffs. The tach zeros when i turn the key on and does spike when i start the motor but does not read anything while running. It's a faria tach that i have ste at 4 which is what a manual i pulled up said it should be. The batteries were charging with the old rectifier. i hven't checked with the new one yet.

From what i have been reading on older posts it sounds like the problem is still with the rectifier because the tach does zero but doesn't track with motor rpms. what would take out a rectifier like this?

 

[mauimike]

Re: tach problems

bump

 

[Reggie08]

Re: tach problems

I'm no expert, but my service manual says for 2-stroke motors, the tach should be set at "6". Have you tried that setting?

 

[Barnacle_Bill]

Re: tach problems

Since the output (red wire) from the rectifier was smoked, there is a very good chance that the rectifier is toast. Common causes are a bad battery, loose/dirty connections. And if you ever hooked up a charger to the battery backwards, even for a split second, the rectifier is toast.

 

[mauimike]

Re: tach problems

I actually checked both rectifiers just for the hell of it and they both checked out good. I also tried bypassing the wiring harnes with jumpers and i still cant get the tach to track with the motor. Where does the signal originate from?

 

[emdsapmgr]

Re: tach problems

Your control box may have a pigtail for connecting a tach already there. The grey wire is the tach signal wire. It gets it's signal from the yellow wire with grey tracer on the terminal board under the cowl. You need a pos wire from the key switch (purple) and ground (black.) Again, look for the wires at the control box. The tach senses pulses from the rectifier and translates them into rpm. Any chance you have the tach wired to the key switch start circuit, instead of a normal hot? Sounds like it may only be working when the key is in start...

 

[tevans720]

Re: tach problems

emdsapmgr is saying it right.

Just hook your own wires up. If you have had a smoked wire there could be others. Try looking for more smoked wires. Then just hook up your own wires. Run a red or yellow wire (just my color preference) from the "I" on your tach to the purple wire in your control box right off the switch. Run a black wire from the "G" on the tach to any ground on the boat. Most or at least mine have a ground right inside the control box for the tach it should be labeled. Finally run a red or yellow wire (differ from the "I" wire you used) From the "S" or "SEND" on the tach back to the motor terminal board. Hook it up to the yellow, yellow/Grey, or the yellow and Grey. In Johnson's I be leave its in slots 1,2, or 3.

Try all 3 slots until you get the right one. Sorry if I repeated stuff you know just being as clear as possible.

 

[Barnacle_Bill]

Re: tach problems

The tach signal comes from the stator via the yellow wires. The rectifier is used as a tie point as these same yellow wires are the input to the rectifier. One of them may or may not have a gray stripe but it doesn't matter which you use. Disconnect all the wires on your rectifier and retest according to your manual. While it is disconnected, test your stator. You might also check the FAQs. I believe Joe Reeves has a post there for testing a rectifier.