RPM Gauge problem.. 2003 correct craft 206. 5.7L engine

[DUG206]

I noticed while driving my boat this weekend at around 3500 rpm(as per the digital RPM's on the perfect pass)the RPM analog gauge is not stable, it moved from aproximately 3500..up to 4700 back to 4200 , down to 3600 and just kept hunting around(at which time the boat was stable and running great in smooth water).
Any ideals on what the issue mght be?
Dug

[Bri93SN]

Do you know if the Perfect Pass is a factory installation? Just wondering if they tap into the same wire...

Actually, hold that thought. I just checked http://perfectpass.com/sites/all/the...Mechanical.pdf It looks like 2003-2005 had a dedicated place for the Perfect Pass RPMs. If you look at item (6) on RPM wire installation.

Maybe you have a bad ground or loose sender wire at the back of the tachometer? Not sure if both tach signal wire originate from the same place on the engine.

[DUG206]

I bought the boat used years ago.. I do believe it was factory installed. I will check for bad ground and sending wire..