I would reduce 1.5"
Hell David, The correct diameter/pitch combination can be determined by comparing the current propeller configuration to the motors ability of obtaining Rpm’s when under load. This is far more accurate then using information from a book. If you throttle up the motor in forward gear, away from the dock, determine the maximum obtainable Rpm’s. If the Rpm’s come up shy to the maximum rated Rpm’s, you will need to reduce the pitch. This scenario often produces black smoke at your top end Rpm’s. In order to determine how much pitch to reduce use a 12% factor. Reduce the pitch in 1” increments and use a factor of 12% for the Rpm’s increase. (Reduce 1”= 3,100 Rpm’s x 1.12= apx. 3,472 new full load) With the current propeller configuration, if you reduce the pitch 1.5” you should see a new full load obtainable Rpm of 3,650 ish. If the black smoke is a result of the overloading of the engine, having the injectors open 100% when only achieving 80% of the Rpm’s causes this. Even after you adjust the propeller to optimum loads you may still have carbon or smoke issues for some time. Because the motor has been overloaded for some time you may have carbon attached to the cylinder walls. You may want to purchase a fuel additive that will help to remove the carbon from the cylinder walls. Valve-Tec makes a fuel additive material that has worked for me. Hope this helps and please let me know if you have any other questions. kwoody@pyiinc.com Kevin
