I had always heard that the most efficient prop would be a 1-blade prop (think: screw). And, yes, a 3-blade generally offers more efficiency than a 4-blade. But a 4-blade (dialed in correctly) would give better holeshot.
There's also the case of prop design and manufacturer. There is a difference - not only in the engineering that goes into the exacting angular design of the prop (think of all the thousands and thousands of angle changes in the blade) but also in the metallurgy of the metal. Cheaper props won't retain there shape as well under load... thereby losing performance and efficiency. Yamaha makes excellent props - so does Mercury.
That said, while I don't have your model boat, I have a much older and larger boat (I'm sure your hull is better designed) and I run a 2-stroke 250HP. At about 3,700RPM I'm running high 27-29 MPH and getting about 10GPH. I top out at 40MPH. I have a Yamaha prop.
Mars, have you had a chance to check your anti-ventilation plate and/or slime growth, yet?
There's also the case of prop design and manufacturer. There is a difference - not only in the engineering that goes into the exacting angular design of the prop (think of all the thousands and thousands of angle changes in the blade) but also in the metallurgy of the metal. Cheaper props won't retain there shape as well under load... thereby losing performance and efficiency. Yamaha makes excellent props - so does Mercury.
That said, while I don't have your model boat, I have a much older and larger boat (I'm sure your hull is better designed) and I run a 2-stroke 250HP. At about 3,700RPM I'm running high 27-29 MPH and getting about 10GPH. I top out at 40MPH. I have a Yamaha prop.
Mars, have you had a chance to check your anti-ventilation plate and/or slime growth, yet?