Originally Posted by madcityskier
I understand how octane works, higher octane, higher combustion point. Less perignition, greater volume in cylinder for explosion= more power. I'm not sure how changing it now could cause a problem. The original PCM service manual and MasterCraft owners manual call for minimum 93 octane, which is hard to come by. The reason for considering is the afore mentioned slight hesitation when getting into the throttle to pull my 285 lbs out of the water, particularly in April and November in Wisconsin. As I mentioned it seems that several mechanics believe this, though since they can't say why I believe it is likely to be an old wives tale.
Is the hesitation always there or only in April November as you state...Cooler air might cause a lean fuel mixture....just enough to cause a slight hesitation under load....
I don't know the 351W's all that well but calling on my knowledge of other issues I had in other engines. You have the ignition control box I assume - which might be detecting ping on acceleration and retarding spark...hence why you don't get the hesitation when using premium fuel.
Could also be a carb issue or carb adjustment.