Spy glad to hear you got improvment with the engine.
The sneezing use to be lean mixture or air leak around the carb/intake manifold.
Before start to adjust the air fuel mixture note the setting you have.
As I mention before 1-1 1/2 turn out from seated is a starting point, not leaner then 1 turn out or you might melt a piston.
No leaner than one turn out? Shouldn't be in the instructions.
That's backwards, turning in less than 1 turn can cause problems.
You start at 1 1/2 turn from lightly seated.
Then warm motor, in gear, in the water.
Turn the screw 1/8th turn at a time.
Wait 10 seconds then turn again.(your using the fuel at the old setting)
When the motor bucks ,kicks, stutters??
Then you turn it back out 1/2 turn.
That's how it's usually done.
The book says:
Motor warm: run for at least 1 min.
Turn the screw out 1 turn
Then running, turn the screw left until it runs rough, misses etc.
Then turn screw in till the motor smooths out, keep turning until it
misfires again.
Then turn the screw back half way between the rough spots.
When adjusting, turn the screw slowly.
Sometimes the motor can suck air causing a miss.
Get it running and spray starting fluid all around the intake side,
keeping away from the throat of the carb.
If the spray causes any difference in the way it runs? then it's sucking air.
On the stbd. side is the fuel recirc system.
It consists of a couple screens that get clogged and cause problems with the idle
and excessive fuel use.
12-13 mph on a 12 with a 6hp That's not bad.
Unless you can figure out what the rpm's are??
That's probably all your gonna get?
What prop? Specs call for 8R9 new.