Tachometer wanders

Stu Jackson · May 23, 2014

Have you checked the connections at the back of the alternator? And the tach?

woodster · May 23, 2014

GCR said:
The tach on my 340 wanders. Engine noise does not indicate it is speeding or slowing down but the tach will wander 500 rpm or more. Has anyone else experienced this and what the fix?

you may have to take the keys away from your tach

seriously though check your connections and make sure they are not corroded or loose all the way back to your tach sensor on the bell housing

this is assuming you have a yanmar

Stu Jackson · May 23, 2014

Another idea: loose or old belt, slipping or too tight.

jdhohmann · May 24, 2014

I agree, If it is a Yanmar, then the tach may be starting to fail, We had ours fail and unfortunately the only way to change it is to do a motor job. I went to shake the wires and the whole assembly fell away in my hands and now I have to re tap the threads. Good Luck:dance::dance:

Cool_Change · May 24, 2014

Ours doesn't wander but never makes it back down the zero even with the motor off. I assume age....

VINN · May 25, 2014

I have that problem once in awhile on my h34. turned out to be a bad ground on the grounding stud on the back of the engine. just loosen the bolt and clean and brighten all the spaded terminals attached to it, and re-tighten. also ck the 2 piece tach connector with a quick reseat. you should be ready to go.

Don Lucas · May 26, 2014

my tach hasn't worked consistently for 3 years, normally works for a few minutes then dies, hasn't bugged me enough to buy a new one as I can tell by speed and sound how loaded the engine is

Cool_Change · May 26, 2014

I'll give it a shot. Thx.