NOTE: Speed ranges vary for different models because of different engine operating ranges and different gear ratios. It is generally best to pick the lowest pitch propeller that produces engine speeds near the maximum engine speed ranges shown in your Owner's Manual. The propeller speed ranges shown are only a guide. More accurate information for a particular boat may often be obtained from the boat manufacturer directly or by visiting the Yamaha web site at www.yamaha-motor.com and checking out the Performance Bulletin section. The best way to select the best propeller for a particular boat and customer is by testing various propellers on the boat.