Saturday, March 22, 2014

Switching to a Feathering Propeller (Max-Prop)

While we're still defrosting from the latest (and hopefully last) snow of the season, we have plenty of time to refocus our efforts, prioritize our upcoming projects, and reflect on some of our favorite improvements we've made to Phoenix thus far; in this case, upgrading to the new feathering propeller.

When Bill motored Phoenix home from Detroit several years ago, the Perkins 4-236 motor had just been rebuilt, a new custom SS shaft was installed, and the boat had a 3-blade, fixed propeller with a 20x10 pitch. She motored very well, but he felt that the propeller was slightly under pitched and there was room for improvement.

Fast forward a few years to when we began sailing Phoenix, and we were listening to the annoying sounds of our fixed prop free-wheeling once the motor was shut off. Bill had installed a feathering Martek prop on our Yorktown Meandrous before we met, so I had never heard the loud whirring of a free-wheeling prop before and I initially thought something was very wrong! We were always pleased with the Martek, but we learned that the 1 1/2" shaft on our Andromeda was too large for their hub design, so we decided to go with a 3-blade Max-Prop Classic instead.

Feathering propellers are not cheap, but there are some more economical ways to go about acquiring one. You can wait for one of the boat shows and see what kind of discounts the companies are offering, or you can do what we did and look for a reconditioned propeller. After talking to the folks at Max-Prop, Bill learned that we could get a reconditioned prop from Max-Prop to fit our needs at a fraction of the cost, and it carried the same warranty as a new propeller. When we ordered it, we knew we weren't going to install the prop right away because of weather and our haul out plans for the boat, so they made notes in our file and didn't start the clock on our warranty for 6 months! Even better, they through in a "cruising package" with 2 extra zincs and 2 tubes of lubricating grease for good measure!

Max-Prop has a great instructional video that takes you step-by-step through the installation process and a great blow-up diagram as well.

One of Phoenix's previous owners redesigned our rudder and changed the propeller aperture, which allowed us to go from a 20" to a 21" propeller. The big question we had was where to set the adjustable pitch. There are many great online tools out there to help you determine your optimal pitch settings based on your boat specs, engine specs, desired cruising speed, etc. Beth and Evans developed an excellent pitch calculator that's available for download on their website under "vessel calculator." And Max-prop has it's own recommendations and charts to guide you as well.

When we used the pitch calculators, we found that we were pretty much right between the recommendations from the folks at Max-Prop for a 14.5 - 16 inch pitch (20 - 22 degrees). We vacillated back and forth, and finally decided to go with the 16 inch pitch (22 degrees). The blades on a Max-Prop are much flatter than you'd find on a fixed prop and from what we've been able to read from other Max-Prop owners, they were much happier when they slightly over-pitched their props. In fact, John from Morgan's Cloud wrote a great article about setting the pitch on a feathering prop. [Note: if you don't want to subscribe to the site, Google "Morgan's cloud" and "feathering propeller" to see the article.]

New Max-Prop, in feathered position
Zinc installed, greased, and ready to go!

New Max-Prop, blades out
Once we splashed Phoenix we were really happy with the new feathering propeller's performance. We can motor 6.5 - 7 knots at about 1750 RPM, and motor sail even faster. 

Motor sailing with the mainsail only, catching an ebb tide under the Bay Bridge at 8.4 knots
The new Max-prop has allowed us to motor faster at a lower RPM, Phoenix backs up much better than with the fixed propeller, and, no more free-wheeling when sailing! We haven't calculated the current fuel consumption yet, but with the lower RPM needed, I'm certain it's better than the 1 1/2 gallon/hour rate that we previously had with a seriously undersized propeller.

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