Re: prop numbers question??
What year engine and is it a two cylinder or three cylinder. If you have a two cylinder both of your current props are wrong. If its a three cylinder they would be in the ball park. The 11-3/4x17 is wrong for the three cylinder but would be ok for the two cylinder. People tend to shop for a specific prop diameter when they should be looking for a prop that actually "belongs" on the year, make and model of their motor. Diameter of a prop is a function of its design not something that makes a 13 inch prop faster or more powerful than a 12 inch or a 14 inch. Prop pitch, rake, hub size (for the specific motor) and other factors influence prop diameter. Check prop listings from the various manufactures for your specific engine and look for those. Just shopping by diameter is going to result in a wrong prop. As a general rule, two identical props (except for pitch) from the same manufacturer will likely have about 1/4 inch difference in diameter. As pitch goes up, diameter comes down and vice versa. Two OEM props for your motor (if its a two cylinder) would typically run a 12-1/4x15 or a 11/3/4x17. Note that as pitch went up, diameter came down because of the blade orientation to get more pitch. Therefore, small changes in diameter have little effect on performance.
