Welcome to the forum.
Has the analysis been completed that identifies the problem to be the sending unit, not something else like the wiring or the gauge?
One terrific aspect about a boat w/ two engines is the ability to swap port / starboard stuff to aid in the problem diagnostics.
If the problem is indeed the sender, then the replacement might require removal of the bad part to match for a replacement.
Many times there is not a clear path above the tank sender, requiring creation of a hole in the deck, hidden behind the side wall.
As would be expected, creation of the new hidden deck hole would require multiple measure twice / cut once steps to ensure an acceptable outcome. That not only includes attaining the desired alignment to the sender, but also to avoid damage to wiring, plumbing and the tank.
There are a few sender options on the old Sea Ray parts web site www.fpmarine.com but it is very likely that a correct replacement may need to b sourced elsewhere.
Having the bad part in hand (if required) is a good first step to locating the replacement.
