Tip of the Month

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To get the most from your boating experience it is imperative to ensure that you have the right propeller bolted on.

It’s via the propeller that your engine pushes your boat through the water, but it’s like using a single speed transmission where you have only one gear, therefore your propeller size – namely the diameter and the pitch – is absolutely critical. The main objectives are to make sure that your boat is reaching and not exceeding your engine’s recommended RPM limit, and that you’re achieving the best balance between acceleration and top speed. So how best can you achieve this? Firstly you need to understand what the key words of ‘Diameter’ and ‘Pitch’ represent. ‘Diameter’ is the distance across the circle made by the blade tips as the propeller rotates, whereas ‘Pitch’ is the distance a propeller would move in one 360° revolution through the water. Your propeller size will be clearly marked on the propeller itself; therefore, if you are using a 3 x 13 7/8 x 19, this means that it’s a three-blade propeller with a diameter of 13 7/8 inches for every revolution made, and that it will have pushed 19 inches through the water.

To check if your current propeller is the correct one, you need to get on the water and run your boat at full throttle – technically referred to as its Wide-Open-Throttle (WOT) point. This will be at full speed at the optimum trim level with a light load on calm water. If you are within 100-200 RPM of your engine’s recommended maximum RPM limit, then you’re running the correct propeller.

If your engine is not reaching its WOT, then you’ve over-propped your engine, the pitch is too high and you’ll need to lower the pitch. If you are over-revving then you are under-propped, meaning that you need a higher pitch propeller. The general guideline is that every inch of pitch will give you +/-200 RPM – lower pitch propellers will bring the RPM up, and higher pitch propellers will bring the RPM down. Application also plays a role, so if you’re carrying a lot of equipment or weight on board or wakeboarding, then a lower pitch option would be best. This will give you more immediate power, a better hole-shot but to the detriment of top speed as the engine will reach its maximum RPM at slower speeds (similar to running your car in first gear only). If you need more speed, for example for waterskiing, barefoot skiing or just cruising, then a higher pitch propeller would be more suitable giving you a greater top speed but to the detriment of rapid acceleration (similar to running your car in third gear only).

Hopefully you now have a clearer understanding of what propeller you should be running on your specific boat!

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