PROPS

Gary Everingham (Info from "the Atomic-4 caster" issue no. 28)

The most popular prop for an A4 is a 12 x 7 which produces 220 lbs of push at zero boat speed and 1600 RPM. At the same RPM you get 155 pounds with a 12 x 6, 250 with a 12 x 8 and 270 with a 12 x 7 CDI performance prop.

Tony Vouvalides, Astarte, #512

I need to change the prop on my Triton due to some damage. It is the original 1964 vintage. It is a 13/8. I saw the CDI ad in Good Old Boat and asked about their replacement. I got this message in return.

"The CDI 12x7 propeller specifically designed to optimize the output of the Atomic 4 direct drive engine. These props have been out in the field for 3 years now and we have received tremendous reviews from the field.

The only time we vary the recommendation from a 12x7 is when there is an unusually large keel right in front of the prop. And, you may ask how we found this out... we tested our prop on a Pearson Triton here and found that the 13" propeller that was on the boat worked better than our 12x7.

In the case of the Triton a 13" propeller allows the tips of the propeller blades to get out into open water. So unfortunately, we do not have a prop that will improve your motoring performance.

Good Sailing,

Julie Femino

Performance Propellers

100 Cummings Center - Suite 160J

Beverly, MA 01915

978-922-2322  978-922-0066 fax"

Davr Butler, Windaway, #175

What CDI say's is true they tested it on my boat(# 175 Windaway) they spent the better part of a day testing my prop and then replaced it with the one they designed for the A4 both under load by pulling the mooring and then at different RPM/Speed I had a very interesting day observing the test but as it turned out my prop worked better because of the keel and dead wood around the prop/rudder opening. Check out http://WWW.atomic4.com/ Tom Stevens has a prop that is designed for our boat.

Rob Squire, #96

I put a three bladed prop on Head over Heels for a while. 12 x 13. When i bought the prop, the shop said the rule was something like 1 inch less in diameter and 1 inch more in pitch.....i can;'t remember exactly. I also couldn't tell you what I put on the boat in the way of pitch of my two blade prop....too much rum, I think! Anyway, 12 x 13 for my Yanmar was too much pitch. The engine (Yanmar 2GM20F) would not reach the power band, and the prop wash pounded the rudder pretty hard. I plan to take the piece to the shop and have it re-pitched to 12 x 12 and give it another try.

Skip Baker, White Cap, #3

When I had my prop repitched, the people at the shop said that the max that a prop could be repitched was about 2", and that was pushing it. They also said that the root of each blade probably remains pretty much the same. But since the root is pretty much negated, I think that someone like Pitchometer could bring yours down to where you will want it. Mine for two blades was about $60-$70. Then if you find that it works, you could get a new prop later on and use the repitched one as a spare...

Larry, Dogstar, #607

I found a three bladed prop stashed away in the bowels of Dogstar when I bought it 12 years ago. I hung it up as a decoration in my garage. When Dogstar's original two blade prop became a one blader I didn't even consider taking the three blade down from the wall. Dogstar's a sailboat. The idea of always dragging two blades through the water bothers me. I bought a bronze two-blade replacement and am quite happy with it. Set it so the blades are aligned with the deadwood.