I didn't vote but I run a 300 vrod on a 24 with a 9'4 beam. I've seen some good fuel burn numbers from Suzuki 300s so I'd say merc or Suzuki but I'm a merc guy.
FYI this might be useful to you...I just stumbled across these diagrams for the Mercury engines. Both the new 4.6L V8s and the "old" 2.6L I6 engines are shown here with all dimensions.
https://www.thehulltruth.com/boating-forum/1031839-mercury-300-4-stroke-dimensions.html
I just bought a new mechanical Yamaha
F250. I’m super happy with it. I’m finding more speed less Rpm than my old F225. Hopefully less fuel burn too. Congrats.
Grady White 228g. Weighs 5500 lbs in the water. Plenty of power. A 300 would great but I didn’t need the extra ponies.