Flexifold three blade pitch

[John Langford]

I have just installed the three blade flexifold prop on my Mark II. After looking over the posts and hearing the recommendation of Dan Tucker  at Flexifold .I went for the 10" pitch

There was one dissenting voice on the list that found the 10" pitch to be overpropped. That dissenting voice is right! I am hittting 6.4 knots at 2000 rpms (tach recently adjusted using electronic tach) and 6.9 knots at 2250rpms. At 2500 rpms the swim grid is awash and I cannot get the engine above 2700rpms (with smoke) when 2900-3000 rpms is recommended in the manual. Dan has agreed to change the blades but I thought others would be interested in my results.

BTW it is a beautiful prop and goes smoothly and quietly into forward and reverse. Still lots of prop walk in reverse. The sailing preformance is excellent with virtually no perceptible drag.

I am a bit surprised that so many other users have not found the 15x10 to be overpropped.

[Jim Hardesty]

John,
When I bought Shamrock 3 seasons ago I installed a Maxiprop and set it at 9.? pitch(I don't have the exact pitch info with me) after one season I changed to 10.? pitch.   Works better for me.  I only have the boat in the water 6 months of the year, so the bottom is always clean.   I'm in fresh water, don't know if that makes a big difference.  I cruise at over 6 kn, can hit 7 kn but the fuel usage goes way up.  I have no problems powering into 30 kn of wind, can go as fast as I want the boat to pound in the steep Lake Erie chop.
I don't know your conditions, but you may want to check your engine.  I set my valves, they were just a little off, but resetting made a noticeable improvement.  And the injectors may need cleaned.
So for me 10 pitch is the best.
Jim

[cmainprize]

Hi Guys
In my experience comparing prop pitch from different manufactures is apples and oranges.  Blade design and surface area are huge factors.  Our Mk11 with the M35A came with a 15X10 2 blade flex o fold.  I never liked the prop, it banged in and out of gear and the reverse was brutal.  It did provide tremendous power.  Too much in my opinion.  The boat would do 6.5 at 1700 rmp and 7.0 at 2100 and start to smoke. The Tach was checked with a laser rpm guage and and boat speed with a gps (two actually).   We were not able to get full throttle.  This prop always gets rave reviews by this board but we were not happy with it.

We swithed to a 2 blade feathering J prop this year.  The blades have a surface area 1.6 times greater then the flex o fold.  The prop pitch is adjustable with no tools (if you don't put in the locking ring) and can be done underwater in less then one minute.  Once you get the right pitch you install the locking ring (but you don't have to).  I had it set up for a pitch of 10 inches and it was a bit much.  Boat speed was 6.5 at 2000 rpm, engine temp is 190.  I dropped it down to 9.5 and the results were great.  6.0 at 1800, 6.2 at 2000 and 6.5 at 2200 with temp of 180.  Full throttle (3000) gave us 7.2 but the temp started to climb.  Reverse is outstanding.  Still lots of prop walk. 

My point is.  Prop pitch is important, but blade design, and surface area are huge factors.  Reduction gear factors are also very important.  The lower the factor the faster the prop will spin.  Put a 15X10 on a yanmar or a volvo with a 2.8 gear ratio vs a hurth with a 1.8 ratio and and the results will be very different.  It seems the flex o fold gets great reviews with the M25, does anyone know what reduction ratio is?  Might be the difference!

Cory

[sail4dale]

Here is my experience ... I changed from a 9 pitch 3 blade fixed to a Flexifold 3 blade 10 pitch.  My speed with a CLEAN bottom and smooth water is about 7 -7.5 knots at a true engine speed of 2375 RPM.  My tach reads slower and I have to factor a 1.25 on the tach reading for the true engine speed so at that speed the tach is reading 1900.  There is no way I can get an engine speed much above that while in gear.   .... any faster RPM than 2100 on my tach and the smoke begins. 

This is  a great speed as in looking at the performance curves on the engine I am running at a nice spot for economy and efficiency.

[Tony Benoit]

I have a Flex-O-Fold on Helen C, and I love it.

I actually like the prop walk (provided I'm coming alongside port-to).  I find that I can come into a pier a little steeper than I normally would.  I put a little throttle on in reverse, and the stern sidles itself right up to the dock.

Happy Independence Day!

Tony
=======================
Helen C
'89 Standard/Wing #903

[Ed Shankle]

John,
Maybe it's the engine size? I've got the m25xp and find 10 works fine. My fixed 3 blade was set to 10 as well.

Ed

[Craig Illman]

Not all the HBW50, HBW100 and ZF10's have the same reduction ratio. That may account for different people's experiences with pitch?

Craig

[John Langford]

Ok folks, here is the skinny on the switch from the Flex-o-fold 3 blade 15x10 prop to the 15x9 version. In my humble opinion the 15x9 is the right prop for the M35 with the normal 1.79-1 reduction ratio gear box. With a freshly calibrated tachometer and a recently cleaned bottom, the boat moves at 6 knots over the water @ 2000rpms and hits about 7 knots @ 2500rpm. Since that is the recommended cruising range of the engine, it works out perfectly. Also the boat will reach 2900 rpms without anything more than the slightest wisp of smoke. Of course, the stern is well and truly buried so who would want to do this for more than a few seconds. The above performance is a vast improvement over the stats for the 15x10 which I reviewed in an earlier post.

The prop is fine in reverse as long as you give it some serious revs for the first few seconds to get it moving. Prop walk is no different than what I expereinced with a three blade Michigan wheel. But if you really want to go in reverse I recommend the Kiwi prop. It stops the boat cold virtually immediately.

Thanks for all the comments and suggestions. I hope this is helpful to future purchasers. I have passed this information on to Dan Tucker at Flex-o-fold who was very cooperative in sorting out the right blades. It is a very good product and he provides excellent service. Don't forget to ask for the 10% Catalina owners discount!

[George Bean]

I am currently in the process of ordering a set of 15X9 blades from Flex-o-fold.  Ordering from their website puts you in direct contact with their headquarters in Denmark.  Keld Willberg informed me that they no longer honor the C34 owner's discount.  Your best bet in the future is to order them during a boat show.  Three blades are $940 including delivery or a little under half the price of a complete set including hub.