Tach Fluctuation at steady throttle

[Fischerman]

My 50 Spl Evinrude at WOT or at any steady speed, has my tach bouncing between 2500 and 5000 rpm. I know the tach is fed off the rectifier and I checked those leads and found no problem including the rectifier output. <br /><br />A mechanic at my local marina, said the problem is probably the powerpack going out (???). Folks, I don't see how that can be. It doesn't make sense. I've never heard of a powerpack failing partially. It either works or it doesn't. Am I wrong? <br /><br />Any help on this would be really appreciated.

 

[heybaylor]

Re: Tach Fluctuation at steady throttle

check the connections on the tach , loosen ,and retighten all of them ..check for "star washer" on the ground connector

 

[Fischerman]

Re: Tach Fluctuation at steady throttle

Thanks for the speedy reply Heybeylor. <br />Sorry, I should have been more specific. I even removed the tach connections just to be sure they wern't corroded. They looked fine, tight and no corrosion. My Clymers book, has no reference to such a problem that's why I'm at a loss and viewing the schematic, I can't see how the Powerpac could cause such a problem.

 

[Ben Konopacky]

Re: Tach Fluctuation at steady throttle

Did the tach. ever track w/o bouncing ? could be a bad tach.or needs some type of suppression, give the mfg. of the tach a call..

 

[katbird]

Re: Tach Fluctuation at steady throttle

Charlie , my tach was the same way when I hooked it up. It would bounce from 2000 to 6000 then to 4000 rpm. I went to the merc dealer and bought a new one and now it reads right on the money.

 

[Fischerman]

Re: Tach Fluctuation at steady throttle

Ben, Ron,<br />Great suggestions. Thanks very much. <br /><br />I'll follow up. A tach replacement makes a lot more sense then a deteriorating power back. Especially if you read the electrical schematic.<br /><br />Again, really appreciate the help.<br />Charlie