-Take it somewhere to be looked at and part with £x, worth getting the compressions checked though.
-I took mine to a local outboard engineers, and they had a tank (instead of muffs) where you could run the engine under load.
-Alternatively (and i will probably get slated for this) if your pretty sure you have fixed the problem. Try out on the water, but make sure you take a friend with you, or just a quiet river somewhere. The only way your going to know if you havE fixed it is by A. a test tank, or B. trying it. I had a Suzuki 2stroke, been there, done it!