| For a propeller to give a perfect fit on a boat, it | | | | increased diameter is fitted on the boat, it |
| should be of correct diameter. When a prop does | | | | increases the torque to run at a specific speed. |
| not help the boat to achieve its optimum | | | | Propellers are available with diameters that are |
| performance, a simple increase or decrease of | | | | usually in one inch increments. Therefore all |
| diameter will solve the problem and provide | | | | measurements should be made in inches. |
| increased performance. The correct diameter will | | | | The Hub diameter is another diameter that |
| depend on the length of the boat, the weight of | | | | impacts the size and performance of a propeller. |
| the boat when it is half loaded, and the maximum | | | | The hub diameter is measured by subtracting two |
| permitted rev of the engine and the planing or | | | | times the blade length of the propeller from the |
| displacement of water caused by the movement | | | | root of the blade to the tip. |
| of the boat. The diameter is also useful to | | | | The use of the boat is an important consideration |
| determine disc area and the disc area ratio. | | | | when increasing or decreasing the diameter of a |
| The ideal diameter of the prop is usually stamped | | | | boat prop. Boats that carry or tow heavy loads |
| on the side of the hub closest to the prop shaft | | | | or are used for leisurely cruising need props with |
| hole. There will be two figures given. The first | | | | large diameters. Cruise boats, pontoons and some |
| figure will be the diameter of the prop. For | | | | fishing boats are examples of boats that require |
| instance if the figure given is 12x11, the diameter | | | | props with large diameters. Large diameter |
| will be the first figure in this case-12. | | | | propellers give greater thrust for slow speed |
| The straightforward method of measuring the | | | | boats. For high speed boats used for racing or |
| diameter of the prop is to use a measuring tape. | | | | other forms of recreation, a prop with a small |
| The distance between the edge of the blade and | | | | diameter is more effective. For slow or calm |
| center line of the shaft hole should be measured | | | | waters in lakes and rivers, large diameter props |
| to give the radius. Multiplying the radius by two will | | | | give good performance. For the high seas small |
| give the diameter of the prop. The general view | | | | diameter props perform better. |
| is that if the diameter is big the performance is | | | | Following the manufacturer's specifications in the |
| better. This is not always the case. The hull | | | | manual for the best diameter for the prop for |
| underbody could create limitations on boat | | | | the engine from the manual is another method of |
| performance based on prop diameter. | | | | getting the diameter of the best performing prop. |
| The other method of measuring the overall | | | | The diameter of a prop is an important |
| diameter is to measure the circle surrounding the | | | | measurement that impacts the perfect propeller |
| prop blades from tip to tip. When a propeller of | | | | fit for optimum performance of the boat. |