Tachometer problem-goes too max and just sits there the entire time. How to check alternator output

Aug 16, 2010
1
Beneteau 343 Rock Hall, MD
Tachometer goes to max and sits there full time after engine start. How to check alternator output or other possible solutions.
 
May 20, 2016
3,014
Catalina 36 MK1 94 Everett, WA
Have you tried adjusting the pot on the back of the tach ( small hole straight slot screwdriver). If that can't bring it down you probably need a new one. To really check you need either a o-scope or frequency meter.

Les
 
Dec 19, 2006
5,809
Hunter 36 Punta Gorda
I had the same problem or at least tack going crazy all over the place and some times calms down and works normal but not always and most times is crazy and new Yanmar tack made by VDO $$$$$$$$$
Found one VDO for $99.00 but it still goes crazy.
Nick
 
May 20, 2016
3,014
Catalina 36 MK1 94 Everett, WA
on my project list is to epoxy some rare earth magnets to the flywheel - and use a hall effect sensor to pick up the pulses - should be a cleaner signal than the alternator.

Les
 
Nov 6, 2006
9,884
Hunter 34 Mandeville Louisiana
The older Yanmars did that with a prox probe counting flywheel teeth which works fine until the old tacho starts loosing its mind.. Don't know what engine you have.. ?
 

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