Christian under 6 kilowatt isn't good for you.
An Atomic is a lot of work. You would be working, to change 4 quarters for a dollar.
Pull the Palmer and try to fix it at home, even run it on a test bed. Little parts can be mailed to you.
Usually 9.9 hp outboards can be 15 hp with only a larger jet in the carb.
In the meantime:
Your 8 hp may do better with a 3 bladed prop, centered on the transom, lower, and maybe a larger jet.
I see why outboards are taking over the inboard market.