If you've already spent the money on the heads, I say run 'em! My 468 runs on 91 octane all damn day with 11:1 compression. The RPM range your boat (or any jet for that matter) is going to spend 90% of it's time calls for a nice flowing, well designed head, outside of a set of aluminum heads, the heads you have are just about perfect.

I agree. My Hondo has around 10.8:1 Compression (according to the math) and I run 91 Octane... but also have a higher overlap cam to help... and my chambers are polished along with detailed pistons.... but they're more of a higher RPM head.... those will work good....