Prop woes

Fellas, I have a 11' mini speed boat that I built. I bought a 07' Yamaha T50 2 stroke outboard that I got for a steal. It has a 9" dia. prop on it now with unknown pitch that goes 42mph on flat water at plane. I was unimpressed with this speed for the size and weight of my boat to size of my motor. I don't know sqwuat bout props and what won't tare the ass outa my outboard. At one site they have listed a 13"X25 prop that could go on boat and a 14"X11 listing directed at my motor size but give no proformance details other than "Duel". Any tips from anyone who has answers to this probem I would be greatful for hints.- The dealer wouldn't give me any help except to point to the Stainless Steel props and say "that will work for you" and not tell me why it would.

What RPM will the motor hit at full throttle ????--------I don't think a 13" or 14 " prop will fit on a 50 HP motor.------------You need a tachometer to determine your optimum prop.

racerone said:

What RPM will the motor hit at full throttle ????--------I don't think a 13" or 14 " prop will fit on a 50 HP motor.------------You need a tachometer to determine your optimum prop.

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Max operating RPM is 4500 to 5500 so about 5000 RPMs is a safe top optimul range according to user manual but the manual doesn't have any max min prop sizes. At USBOATSupplies is where they list the 14X11 Duel prop.

What RPM are you running at right now , at full throttle ?????-----------------Is your motor a " high thrust " model with a bigger lower unit than a standard 50 HP ?????