Marine engines work mostly at one rpm, governed by the propping . And they have water-cooled manifolds. You might be able to get away with wide seats in that marine application, but
would you have much success in an engine that is gonna see many and diverse throttle openings? I think you would be better off controlling cooling in the usual ways. IDK, I'm just thinking out loud.
But cruising at just 2400, the exhaust valves will have plenty of cooling time..... especially if you can figure out how to get the mixture to all burn in the chambers, beginning with providing an early enough spark. That's gonna be key.
by any chance, can you post a pic or two of that unit? I'm wondering what you actually have, and how heavy it is. And most of all, how it presents to the wind.
