Boat propellers are the most important part of your boat. They control the speed, direction, and power of water flow. If you want to know how big your boat’s propeller needs to be, you can start by measuring the diameter of your boat. The YouTube video “How to Find the Size of a Boat Prop” details the steps to follow to find the size of a boat prop.
To find the size of your boat prop, measure the diameter of its shaft. This part runs through the prop gear casing and is usually made of steel or aluminum. The shaft will be round, but it may have a slight taper.
If you can’t find a ruler that measures in inches, you can use another method to calculate its diameter.
First, draw a circle with a pencil on paper. Then make a mark at one-third of the diameter of your circle – this is the distance between two marks on opposite sides of your circle (called “paddles”). Next, measure from one paddle to the other and multiply that measurement by 0.33). This gives you an approximate value for your prop’s shaft/prop diameter ratio.
You can also use a tape measure to determine this ratio if you don’t have access to other measuring tools or methods. Make sure that you measure each end of the tape separately so that they are even. Otherwise, your numbers may not be accurate enough for calculations.