Those boats were designed so that if you got bored with it, you can make it Sport 20 legal. It takes a bunch of work of course but it will take the power.
Check
www.novarossi.us to see if Glenn Quarles has something that you might like. Even his .12's put out a lot more power and RPM than many others.
Here's a bolt-in:
https://www.novarossi.us/collections...x15pr-15-motor