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

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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.

CAP­TAIN’S TESTS ON­LINE Test your knowl­edge of boat­ing with more Cap­tain’s Tests at boat­ing­mag.com/cap­tains-test.

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