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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Gas > Atomic 4
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Old 04-24-2012
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propeller suggestions

my prop might be too small, anyone have a suggestion for a Pearson 30 with an atomic 4? I was thinking about a 3 bland prop, there was just no power with the current 2 blader I have now.

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cbarison
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Old 04-24-2012
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propeller suggestions

I highly recommend the Indigo 3 blade. Just make sure you use a zinc ( indigo states otherwise).

I have a large 2 blade if you are interested. PM me if so.
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Old 04-24-2012
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Re: propeller suggestions

What are your issues? lack of speed at rpm? can't rev to normal rpm? high revs and no 'push'? Is the prop clean? is the hull clean?

As you can see lots of issues that need to be clarified before any meaningful advice can be offered. However if you're going to reprop and don't want to spend on folders/featherers you might want to consider a 3 blade Campbell Sailor prop.. a reasonable compromise cost and drag-wise.
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Old 04-25-2012
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Re: propeller suggestions

Some other variables need to be aired.
Which boat make/model is it? Displacement(weight)?
Does it have a prop in an aperture before the rudder or is it a free standing prop?
With a strut or no strut?

You'd likely see a performance improvement with either the Indigo 3 blade prop designed for the A4 or a Campbell Sailor prop as mentioned.
The hull shape and design of your boat does make a difference though.
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Old 04-25-2012
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Re: propeller suggestions

Keep in mind that most A4s are direct drive which means a smaller and finer pitched prop due to the higher prop RPMs. Do you know the pitch and diameter of what you have now?
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Old 04-27-2012
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Re: propeller suggestions

A 12 X 8 Prop is a bit BIG on a healthy motor and you a VERY have limited selection ,i will be testing a 12 X 7 flex-O-fold within the next two weeks and i hope it works as its mine now

My 29" 8000# Cal is happy at 1400 RPM and goes 5.5 to 5.8 Knots in pretty much any wind below 30 knots

While it will go above 2000 RPM with the 12 X 8 it just pushes the stern DEEP underwater which gets your feet wet and BURNS twice as much fuel to go 6.8 Knots so IMHP its kind of pointless

One of the issues is while the motor is rated at 30HP/3600 RPM that's a bit of a self-destruct RPM as I have not seen them run much over 2200 RPM


The prop slip % on displacement hulls is always real bad and only gets worse as you ramp up the RPM
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Last edited by tommays; 04-27-2012 at 04:24 PM.
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Old 04-30-2012
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Re: propeller suggestions

Another thing to consider with A-4's performance. For the last 4 years I have been sorting out the performance of our Islander-28 which now enjoys a "new" fw cooled Moyer rebuilt A-4 sporting a Indigo 3 blade prop. Along the way, 2 years ago, with its new engine I couldn't get the rpms up to spec. I had a 2 blade prop and was wishing for more reverse gear response, too. I installed the Indigo 3 blade. More effective reverse but still not right. I really lucked out when motoring back to NEH for a November haul out. The hull was bearded and I was not expecting performance. The wind picked up to 20 knots no the nose. I was creeping along. Shortly after turning to starboard and entering the protected mouth of the harbor the engine died. A passing boat helped me to the dock. That was the lucky part. The hot pipe had cracked. I did not replace it when I replaced the engine. It was a ss assembly and I ASSumed it was O.K. NOT! It was nearly half blocked. I have replaced the entire exhaust and rpms are fine. Could your back pressure be too high?

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Last edited by downeast450; 05-01-2012 at 06:32 AM. Reason: sp
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Old 04-30-2012
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Re: propeller suggestions

I second the 3 blade Indigo prop. It's optimized for a P30/Atomic 4 combination.

I put one on my old Pearson 30 and it made a huge difference both ahead and astern. Since encouraged 2 other Person 30 owners to do the same and everyone's been really pleased.

It's a pretty inexpensive solution that I think you'll be really pleased with.
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