1982 Grand Banks will most likely have the Ford Lehman which does not return much fuel at all. The engines themselves will not do it.
Separate system is better or modify the tanks with a drain port. It will tell you if contamination is present although it may not be able to get it all. If low enough the contamination can be detected before it reaches the engine fuel pickup if checked often enough.
Most of us do well with GOOD and adequate filtering. A single Racor may be good enough or not good enough. But with some care & thought you can be well protected.
Go to Seaboard Marine and read his suggestions. www.sbmar.com
. and learn. Even Tony points out you do not have to junk what you have but modify to substantially improve
what you have. He has the experience to know better than most of us.