Same boat, bran new engine, I just rebuilt the entire thing. everything is set properly, and i have noticed the more its run the more power it has. All is set correctly, timing and all. runs great. its a 20' bayliner. Last night i put 1 gallon 50:1 in with my 20:1 mix, it backed it into the water keeping it on the trailer, started it checked with a timing light at wot for a second and it literally picked up the entire trailer. I think its running as it should it was just the gas mix and not being run much yet.
I literally do not even have a hr on it yet. Tonight if the weather is nice i will mix 20:1 like it was (taking the performance hit) to continue breakin. I am fairly confident its where it should be now.