View Full Version : Some Prop Questions

07-21-2005, 05:23 PM
What does the size mean(such as 12.5x13 vs 13x13)?
What happens if prop is too big?
What happens if prop is too small?
My prop was fixed, but I am going to get a spare.
Just trying to learn as much as I can.

07-21-2005, 08:36 PM
To answer your questions. The first number in a props size is the diameter the second number is the pitch. Usually you would never change the diameter of the prop but a change in pitch will give you many performance difference. Generally the lower the pitch the faster the prop will spin and the quicker it will get up to speed. The opposite is true with a higher pitched prop. If the prop pitch is to high (big) the motor will not be able to turn it for optimum performance. Only being able to spin lower rpm and have no hole shot. To low a pitch and you can over rev the motor and also blow out the prop (spin it to fast to quickly cavitating it) There are many other variables and obviously the above is true to a point.

If you are looking to get a new prop I would highly reccomend getting a new CNCd prop by either Acme or OJ and use your current repaired prop for your spare. Call either of the companies up and ask them for a reccomendation for your particular application. They are very knowledgeable and the performance difference is amazing.

Also type PROP into the search function of the board. You will get more information and prop tests than you will probably want to read. Have fun....

07-21-2005, 09:12 PM
This West Marine article is helpful: