The Chrysler flathead 6 was used quite a bit as a marine engine. I believe it was sometimes called the "Chrysler Crown". I have operated a boat with one.

As far as meaningful hop up, not a good candidate. Long light rods, very close siamesed bores on the 230 and limited breathing.

You can get a moderate cam and some guys have installed dual carbs. Either or both might help a little. I run the cam in a PW. It seems to help a bit between 2500/3000 RPM which is really rolling for one of these guys.