OldReliable writes:

how much work would it be to install a new gas guage in my '95 18ft
Neptune fishing boat?

You mean a fuel tank sending unit. The gauge is the thing on your
dashboard.

These things are short-lived, as is obvious if you look at how they are
constructed and consider the constant motion they endure. And as is
obvious if you consider the rapid turnover of spares at the chandler's.

So a proper boat makes this an easy change-out. You should have an access
panel to get to it and to inspect your tank for corrosion. The replacement
sender kit will have the instructions you need.