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.

 

[Barnacle_Bill]

Re: Tach Fluctuation at steady throttle

Yes power packs can gradually die just like any other electronic component. The tach actually gets its signal from the stator which also feeds the rectifier. Before you run out and buy a power pack, disconnect all the leads from your rectifier and check it according to your manual. If one of the 4 diodes opens, you will still have some output but the tach will operate erratically.