Re: Need new/spare prop
There are many places you can get a new prop, including right here on iboats. You will need to know the size and pitch when ordering. What is the year and size of the motor , or model number? If not badly damaged, your current prop can be repaired, or re hubbed if it is spun for much less than buying new. Does this current prop bring your boat to the reccomended rpm range at WOT?
The goal in prop selection is to determine what propeller style and size will maximize performance for your boat, while allowing your engine to operate in the recommended RPM range. The correct propeller will prevent the engine from over-revving, yet allow it to reach the minimum RPM where maximum horsepower is produced.
If when running at WOT you over-rev the engine, you need to increase the pitch of the propeller. Increasing the pitch increment by 1" will result in approximately a 200 RPM drop. If when running at WOT shows, however, that you are only able to obtain a RPM somewhat lower than the maximum rating given by your engine manufacturer, you would need to decrease pitch. Decreasing pitch would increase your RPM.
You also mentioned a cupped prop, switching from an uncupped to a cupped propeller will also reduce your RPM. The cupped propeller of the same pitch and diameter will typically reduce your RPM by approximately 200.
Once your wide open throttle RPM falls within the recommended range of the engine manufacturer, you have a propeller that is suited correctly for your boat with respect to RPM.
