tachometer

In March of 2020 we purchased a new 2019 Bennington 21 SSRCXP we took delivery in early April and I noticed multiples issues which the dealer resolved with the exception of 1. I noticed with the engine off the tachometer registers roughly 900 RPM. I have owned a number of boats in my...

When I start the motor the tach needle does almost a 360 degree travel and points directly down.  And there it stays. Does anyone know what this means?  Is my Tach bad?  Or is it not receiving signals from the sending unit? Thanks for your help on this.