DIVE WATCHES COMPARED

Your propellers are the transmission of your boat; they convert the engine’s energy into propulsion and movement. This captain’s test will help you with propeller knowledge. How much do you know? —John Tiger

1. How would you measure the diameter of your propeller? A. The diameter is the distance measured across any two opposing blade tips to the outermost points. You’d need to use a tape measure and measure around the blades. B. Who needs to? It’s always stamped somewhere on the prop. C. It’s the distance from the center of the hub to the outermost tip of one blade, times two; measure with a tape measure or ruler. D. None of the above E. A and C above

2. What is propeller pitch and how is it measured? A. The color of the propeller, measured with a spectrometer. B. The distance a propeller would push a boat through the water in one complete revolution, minus a certain percentage for slip. C. The distance around the blade tips, measured with a cloth tape measure. D. None of the above

3. What type of propeller would be best for a semi-planing hull such as a large cruiser or underpowered pontoon boat? A. A cleaver propeller B. A four-blade propeller C. A propeller with low pitch, large diameter and large blade area D. A jet-boat impeller

4. If your propeller is damaged by an underwater strike, what’s the best way to repair it? A. Don’t repair it. Buy a new one. B. Paint it with factory marine paint. C. Have a qualified repair shop assess the propeller and drive for damage, and repair if possible. D. Straighten and weld the blades, then balance them.

5. What’s the best way to select a propeller for your boat? A. Use the factory propeller selection guide to start; then, using your

tachometer and speedometer, dial in to the best performing propeller by testing several examples. B. Buy one from the internet. C. Visit your dealer and ask for help in testing and selecting the propeller that performs best for your application in your typical operating conditions. D. None of the above E. A and C

6. What should you do to inspect and maintain your propeller at the end of each season? A. Remove it and check the propeller and propeller shaft for straightness and damage. B. Have a qualified repair shop perform any necessary repairs in the offseason. C. Remove any fishingline snarls from the propeller shaft, and apply marine waterproof grease before reinstalling the propeller. D. A and C E. All of the above

1. E. A and C are both correct, although C is the easier and more accurate way to measure.

2. B. Pitch is defined as the distance a propeller would push a boat through the water in one complete revolution, minus a certain percentage for slip.

3. C. A propeller with large blades, large diameter and low pitch would be best in this application.

4. C. Not many boaters have the skills, tools and experience to repair their own props. If you don’t, bring it to a pro.

5. E. A and C are both correct, although if you’re not very experienced in gauging propeller performance, working with your dealer is likely your best bet.

6. E. All of the above are great propeller and drive maintenance tips for the offseason.

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