Whacky tack problem

[dimock44]

The tack on my 1991 Evinrude 60 hp is very erratic running between 1 and 2000 rpm at trolling speed, the slowest possible. One time it jumped to over 6500 at wot. Mostly it bounces around at any given throttle setting. My thoughts are to clean all the connections. Where does the tack connect to the engine? What sends the electrical signal from the engine to the tack? From reading and searching it seems to come from the rectifier on some engines. When rectifiers fail do they burn out or can they give erratic readings while failing. The battery stays charged. Could the tack be bad? My wiring diagram doesn?t show a tack. Any thoughts or insight would be greatly appreciated.

 

[Silvertip]

Re: Whacky tack problem

If your thoughts were to check connections, then that would be a very logical place to start. Check the connections on the back of the tach. While you are under there, there is a calibration dial on the back. Note the current setting (probably 6P) and then turn that dial back and forth a few times and reset it to 6P (if that was the original setting). If you have a control box mounted to the side of the boat, check below the key for a three pin plug. The tach is probably connected there. One wire from the engine provides the pulses the tach is counting. It comes from the regulator/rectifier. +12V, Ground, and the instrument light are all fed from the console via the ignition switch and panel light switch.

 

[dimock44]

Re: Whacky tack problem

Silvertip
I cleaned all the connections and rotated the pointer dial like you advised. I also removed th rectifier and cleaned all the connections. That seemed to settle the fluctuations and all was normal until I looked down at the tack while taking off and it was up around 6500. I had a boat full and was giving it a lot of throttle Could this have been prop slip or cavitation? Also do rectifiers go bad all of a sudden or sometimes intermittently

 

[emdsapmgr]

Re: Whacky tack problem

I'd replace the rectifier. They fail in peculiar ways. I ran a 1991 60 hp on my pontoon for 2 years-always kept the battery charged. Mostly just above idle-1800 rpm. Finally installed a tach. The new tach would act up over 3000-go up to 6000, then finally go to zero. My read is that it functioned and charged properly, till high rpm's. Yours could be the same.

 

[dimock44]

Re: Whacky tack problem

Thanks emdsapmgr. I was thinking about replacing it just to be sure.