One advantage of a gas boat is the engine does not loose as much efficiency as a diesel when slow speeds are called for.
A modern OB 4 stroke will be a car engine design , as is, or shrunk for the smaller output.
60hp pulling skiers up fine , but throttling back to perhaps 10 hp for trawler crawl speeds for this boat will not bother the engine.
With modern complex engines, gas can create 13-14hp/gal , very similar to what an underloaded diesel would create.
And gas IS cheaper than diesel,,,And one heck of a lot quieter.