Ive got a 2004 mudbuddy longtail w/ 25 hp kohler engine that loses power when under a load in the water. Seems to have full strength once the prop is removed from the water. I don't have a tach gauge so I dont know what the rpm's are at, but there is a noticable difference (more than normal) when the throttle is around halfway. Just rebuilt the carb and replace seals and bearings, but that didn't help. The prop is fairly old and has some decent wearing.

Thinking of replacing the prop, but before I spend the money do you think this is my problem?

Getting a prop with good bite will only exaggerate the issue if you're having one. I'd suggest spending less on a tach first and going over all your fuel lines and making sure they're in good shape with no leaks, clean filters, and verifying your tank is venting like it should be.

Once it's running the way it should be, if your prop is worn, you'll have speed issues and turning TOO MANY RPM. Not too few.

Thats what I thought too, thats y i was hesitant on buying a new prop. I forgot the mention, I have my fuel tank located in the bow with a water/ fuel seperater. I have tried bypassing all but 2 ft of fuel line and removed gas cap to ensure ventilation, but with no improvement.