Originally Posted by rwidman
The point is, the water is supposed to stay on the outside of the boat so unless it has sunk, there should be very little difference,
The exception would be an I/O (stern drive) but few trawlers have these.
There is a huge difference. You will never hear of a fresh water boat having to cut out corroded fuel tanks (frequently discussed on this forum), discard corroded air conditioners, corroded hydraulic pumps or replace corroded wiring.