tachomter tach test

Has anyone tried using a 2000 Challenger 1800 tachometer in a 1999 Challenger 1800 boat? Both of my tachs are not working and I wanted to hook up a working 2000 tach to begin diagnosing if it is wiring or tachometer issue.

I have a tachometer off of a 93 xp. It doesnt have a connector in the middle and has to be wired directly in the electrical box. I cant remember if it works. Is there any way to test a tach with a multimeter or something without another seadoo to hook it up to? Thanks