there are a lot of possibilities here
start with checking the float levels ,
make sure the choke is only closing lightly or not even all the way .
is it boiling the fuel when you shut it down , possibly you need to block the heat crossover port in the intake
just push the pedal 1/2 way down before you start it cold to set the choke
& yes the outboards do play a roll , they have mixture screws in the base plate also