I have a 1995 30 hp. merc. looks like everything is the same as a 40,except for the carb. a 30 has a 54 jet, and a 40 has a 66 jet. is that the only difference,or does the 40 take a larger carb? the boat is rated for a 40, and I may want to convert the 30 to a 40,either by larger jet or...