What is the max rpm rating of your motor ? How many rpms are you turning with a near empty load ? Did you buy the boat like this or has it gone south over a period of time? Some people put a higher pitch prop on there boats thinking that it will increase fuel mileage and it does just the opposite because all your doing is lugging the engine. Compression numbers and timing are two other factors. A 3 bladed SS prop will give you a 1-2 mph gain in speed and a smoother troll in most cases vs a flexed out old aluminum prop. No one can give you a definitive answer with out some basic info. You can have props repitched by most reputable shops. So if your running a 19" and are 1 or 200 over the redline they can make it a 20" so your a bit under it. Where as a 21" would be too much and your back to lugging her.
