Bad Tacometer, Spe or wiring?

[Nelsonhow]

The tach on my 1983 Hunter (2GM) motor reads almost e actly 1/2 the actual RPM. This is the original tach and it's exposed to the elements on a vertical cockpit wall. (I checked the RPM with a laser at tach.) the wires look ok as far as can tell.

Any advice on how to diagnose the problem? Can you put an ohm meter on the leads of the tach or something

 

[woodster]

The tach on my 1983 Hunter (2GM) motor reads almost e actly 1/2 the actual RPM. This is the original tach and it's exposed to the elements on a vertical cockpit wall. (I checked the RPM with a laser at tach.) the wires look ok as far as can tell.

Any advice on how to diagnose the problem? Can you put an ohm meter on the leads of the tach or something

it probably about dead based on the history you offered and the exposure for about 85 dollars you can replace it with a wema tach that will work on you flywheel pickup sensor may be a little higher but not much and it will be with in 3 rpms of on the money

 

[kloudie1]

2GM Tacho

Here is what the original looked like..Could be getting bad, but exactly half reading is strange.

 

[Nelsonhow]

An update of success....

Waited for a new OEM Yanmar 2gm P=97 tachometer qto come up on ebay. About 1/2 the price as from the dealer. Installed it last week and TADA , success. tach reads about 3,800 RPMs at MAX throttle.