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Tachometer Problem

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olddawg

Contributing Member
Not sure, but think I may have a Tachometer problem. When I turn on the ignition key my tach needle jumps up to 2000 rpm. Neither the engine or anything else is running. Never seen this before and would appreciate some help in figuring this one out.

VP 125A with Pentronics Electronic Ignition and Flame Thrower Coil.
 
Does it work OK when engine is running?
And my usual standard question...
When did this problem start or did this engine/tach always have this problem?
This is a recording...(click)
 
Sorry to jump into your thread. I have a similar problem. Tach jumps, increases with increasing revs. Problem has gotten worse with time, now it affect temp gauge and alternator gauge too. AQ 120b, petronic electronic ignition.
 
Crappy connection between the ignition switch and the +12V feed to the instrument panel. Also possible bad ignition switch. Possible bad connection of +12 from the battery TO the ignition switch.
 
Most of these 4 cylinder engines have the ignition coil installed just above the bellhousing, and they get wet with rain or sea water coming from the end side of the engine cover. The first symptoms of humidty/corrosion are hard starting (mainly with points) and tachometer readings all over the place. That is why many people have removed the coil and installed it attached to the transom, where it is nice and dry.

Make sure the connections at the coil are clean and tight, then cover them with dielectric grease or vaseline.
 
Thanks el pescador. Moving the coil sounds like a smart idea. Think I'll do that. By the way, the tach problem is solved. I cleaned and tightened all connections at the coil and the tach and all is now normal again.
 
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