Tach bouncing

[godric]

I have a 2004 Mercury 90hp 4-stroke on a 1750 crestliner fishhawk (Faria gauges). Occasionally at lower RPMs the tach will bounce quite a bit. Sometimes at WOT the tach will also start bouncing (Roughly from 2000-7000 RPM). When it is bouncing, I do not hear the motor revving or dieing. Any ideas what this could be and how I can fix it? It is an occasional problem, which I know creates problems in identifying or fixing it.

 

[Chris1956]

Re: Tach bouncing

You may have loose electrical connections on the tach.

 

[tashasdaddy]

Re: Tach bouncing

the tach operates of the rectifier. sounds like a loose connection, or rectifier going bad. being a 2004 i vote loose or corroded connection.

 

[drewpster]

Re: Tach bouncing

I am not sure of the technology here so take this with a grain of salt.
If the engine has an ECM (electronic control module) or computer, the gauges are most likely driven by it through a separate control box. We have had a bunch of problems with gauges going bouncy due to bad gauge driver boxes. However I am talking about a whole different animal (not marine) so don't hold me to it.