2005 290XLS gas guage shows full...

[Blackman]

2005 290XLS gas guage shows full .. then goes to empty after a while, last time had half a tank.  any tips ?

[wingless]

Welcome to the forum.

The problem is either wiring, sender or gauge.

Each may be individually tested to identify the source.

Lots of online tips for fixing, here is one.

https://www.boatingmag.com/checking-boat-fuel-guages-and-fuel-sending-units/

[Hugo]

If you have trouble filling the tank - have till slowly and it bubbles, you may have a problem with the vent.