Considering that probably the best ever gas in-line 6 is the Ford @ 300cid.
This brute displaces 409cid.
I can easily see it in trucks, busses and some stand-by generator use.
I don't see marine use,,,, yet..
Running on LP or natural gas could be an interesting option with minimal changes.
EPA certification was back in 2021.
High pressure common rail and turbo charged.
Not by much but maybe skinnier than a V-8.