Boat Propeller Pitch

Boat Propeller Pitch

The type propeller on your boat motor can make a big difference on how the boat performs. The propeller that comes with the motor may not be the best for your boat. Two blade props and the pitch of the prop can make a major difference.

As a rule, a 2 blade prop is more of a speed propeller and a 3 blade prop is more of a power propeller. Somewhere on the prop is usually a pitch number for the prop.  A 12 pitch prop pushes the boat forward 12 inches each turn. How they come up with the number I have no idea, but it gives you a way of comparing different props.

Because a two blade prop has less mass and less blade surface it can be turned faster by the motor and it cuts into and pulls the boat faster through the water. A 3 blade prop  has more surface area for the same diameter as a two blade prop and has more pushing force as it turns.

I have two trolling motors, one that is a 40 thrust with a 3 blade and a 45 thrust with a two blade. The props are the same diameter and they are interchangeable between the motors.

I use the trolling motors for the most part, to move my sailboat from the dock to open water and back after the sail. It is a small but heavy boat so I used the 45 thrust motor on it. After I lost the two bladed prop in a weed mat one afternoon I put the 40 thrust motor on the boat till I could order a new prop.

I found that the 40 thrust motor worked as well or even a little better at moving the boat then the 45 trust motor did. My first thought was that the 45 was on its last legs and was time for replacing. Then as a lark, I put the 3 blade prop on the bigger motor to try it out. I did not want to buy a new prop for a motor that was on its way out. To my surprise the 3 blade prop on the 45 made a noticeable difference in moving the boat. The motor was OK, and  the 3 blade prop made a big difference.

So what I had found was the 40 thrust motor with the 3 blade prop worked as well as the 45 thrust with the 2 blade prop. And by putting a 3 blade prop on the 45 thrust motor I got better results with the little motor on my sailboat.

The weight of my boat has a lot to do with it.  Both motors on the dinghy with stock props work great. The power thrust difference is noticeable in the dinghy between motors. But the props make the difference when they are used on the heavy sailboat. I would not have thought the prop pitch and type would make that much difference.

If you are not happy with how your boat is handling, try a different type of prop on the motor before you go out and spend big bucks on a new motor. Go to a dealer and ask if you can try a few different props on your boat to see if you get an improvement. If you don’t get better results he will be more than happy to sell you a new motor. 8-)