gas gauge

New owner of a 2011 22SLi, Yamaha F90. Very familiar with the "one-third out, one third back, and one third in reserve rule. That said, I'm curious about the accuracy of the fuek gauge. Any thoughts? Thanks

My 2014 Bennington SSRX is intermittent on the fuel gauge.  I started noticing it last season.  Now it shows full most of the time even though I know it is at half or 3/4s.  Anyone have any thoughts as to how to diagnose or fix it?  Too new to have problems already.