I have a Ford 2712e in the boat with the Bowman FH 440

I have also lying an additional heat exchanger type Bowman FH440-3404
which is intended for fresh water cooled exhaust.

I thought to shine this up to swap with the one standing in the boat. But I have salt water cooled exhaust in the boat.

Can I then plug them in and out of freshwater cooled exhaust?
Or is it better to switch to freshwater cooled exhaust?