# Pros and Cons of Folding Propellers:Avoid J Props



## Melrna (Apr 6, 2004)

I am starting this thread for two reasons. My utter disappointment in my feathering propeller,* J Prop*, and "Buyer Beware" of performances gained and lost when putting on a folding/feathering propeller.

Folding/Feathering Propellers are expensive. Average price is anywhere from $2-3000 plus haul out and install. Most require that you cut the shaft at the end of the threads. If you ever want to go back to your old propeller you will need to buy a new shaft.

There are many reasons why a sailor would consider putting on a folding propeller. Performance enhancement while sailing and reverse operations. These two enhancements are what all the salespersons who sell folding propellers tell you. What they don't tell you is the other side of the story: motoring. Most if not all folding propellers lose power, the ability to propel your boat as fast as your fixed propeller. How much is lost will depend type of boat. 
For racing boats, they don't care because they are not using the motor much except to get in and out of the dock. Racing boats want the least amount of drag so most go with a 2 bladed folding propeller. Same can be said with most sailors that just daysail their boats but desire more performance while sailing.

Cruising Sailboats - Those sailors that are full-time/part-time cruising, and/or with heavy displacement boats and need all the performance they can get while motoring should consider not putting on a folding/feather propeller. Major power losses of up to 1-2 knots could result in putting on one of these propellers. With my J Prop I have seen losses of up to 2 knots. 
So one would ask, "Why would I care about loss of power while motoring"? Several reasons. The obvious is you are going slower and need to get somewhere. A lost of 20%-30% of your boat speed is serious business. That is a lot of lost horsepower. Second reason, big seas and big wind. You will need that horsepower to overcome these. Backsliding down a wave front is not fun and very dangerous. This happened to me in St Augustine Inlet. We almost broached. This happened on a 7' breaking wave. I didn't have the horsepower to get up and over. 
So lets look more closely at why a feathering/folding propeller losses horsepower. Simply, flatter blade design. They need a flatter blade design vs a fixed propeller to do what they do best; fold/feathering. With a flatter blade design each blade cannot produce thrust at the same RPM as your fixed blade can. Since sailboats have very slow RPM's vs a motorboat, our blades need more camber to produce the required thrust to move our sailboats. The same analogy as sailing with little wind vs high winds, we need more camber out our sails in light air conditions: Slower RPM =light winds requires more camber. 
To get the same about of horsepower in a folding/feathering propeller you need to get more surface area somehow: usually a bigger size propeller. Most sailboats do not have the clearance to do this. One has to be very careful here and not get the blades to close to the underside of the sailboat to prevent cavitation.

In summary, the pros of a folding/feathering propeller, less drag while sailing and better reverse performance when docking (no or little prop walk) Cons: loss of horsepower while motoring and expense. 
The big question: Is gaining .25-.5 knots sailing at certain wind speeds and angles worth the loss of 1-2 knots of motor speed?
For me a fulltime cruiser, NO. A big mistake on my part or I just bought the wrong feathering propeller.


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## Maine Sail (Jan 6, 2003)

Melrna said:


> I am starting this thread for two reasons. My utter disappointment in my feathering propeller,* J Prop*, and "Buyer Beware" of performances gained and lost when putting on a folding/feathering propeller.
> 
> Folding/Feathering Propellers are expensive. Average price is anywhere from $2-3000 plus haul out and install. Most require that you cut the shaft at the end of the threads. If you ever want to go back to your old propeller you will need to buy a new shaft.
> 
> ...


I guess I am confused because you keep saying "folding propeller" & the J-Prop is a feathering prop similar to the Max-Prop or Variprofile.

Something is clearly not right.

We also run a J-Prop and it has been one of the nicest props I have owned or run a boat with. Smooth as glass, great power, a bit faster under sail, and stops on a dime. You would need to pry this prop from my dead fingers but I could not get rid of the Flex-O-Fold fast enough..










On this same vessel we have had a Michigan three-blade, Campbell Sailor, Flex-O-Fold two blade, back to Campbell Sailor (when the FOF did not work out) and now the J-Prop which has been absolutely flawless.

We suffered ZERO speed hit compared to the CS and the Michigan, can still hit max rated RPM, and we sail slightly faster in lighter winds than we did with the CS and Michigan. If anything our speed under power may have gone up by .1 - .2 knots but this is hard to quantify. The surface area of the J-Prop is likely leading to less "slip" that we had with the Campbell.

Sounds like a sizing or pitch issue which on the J-Prop takes about 40 seconds to remedy, if you launched it for "set up" without the pitch adjustment locked down......

Have you discussed this with Stanley at Beta Marine?

Again, we have had a ZERO performance hit with our J-Prop and I am very, very, very picky on this stuff. It has honestly been the finest prop we have had on this boat in terms of performance, sailing speed and smooth.

Perhaps you are just under pitched or it was sized wrong......


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## outbound (Dec 3, 2012)

Been very happy with 3 blade max prop on current outbound and prior PSC 34. Have heard "not so much" with 4 blade version. Although burned 106g going and 100g coming back from Carribean would note we sail not power 95% plus of the time over the course of a year. So yes that 1/2 to 1 kt. sailing is a very big deal. We will turn on the engine when VMG goes below 5kts. So again that 1/2-1 kts.. is a big deal.
Respectfully disagree with you on that point.


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## Faster (Sep 13, 2005)

I have to go with the two gentlemen above.. our 3 blade MAX has in no way impacted our performance under power except for the better, and under sail performance is much better indeed. It's hard to imagine why you've been so affected.

Your point about needing to modify the shaft has some validity.. though I think I could still mount my old fixed 3 blade but couldn't 'double nut' it anymore.


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## capecodda (Oct 6, 2009)

I've also had excellent luck with MaxProps on my last 2 boats. Lot's of power to push through a seaway, and absolutely excellent reverse. Never had a problem in 17 years, and would recommend them.


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## Melrna (Apr 6, 2004)

Mainsail - I have talked to Stan many times on our issue. I have gotten nowhere. The prop has been professionally installed and the pitch has been matched with the engine RPM's. Took 4 times (read Haul Out) to get the right settings due to Stan initial miscalculations.


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## Maine Sail (Jan 6, 2003)

Melrna said:


> Mainsail - I have talked to Stan many times on our issue. I have gotten nowhere. The prop has been professionally installed and the pitch has been matched with the engine RPM's. Took 4 times (read Haul Out) to get the right settings due to Stan initial miscalculations.


The beauty of the J-Prop is no need for a haulout to adjust pitch... I dove on mine twice to get it just right and each dive was simply holding my breath.

Sizing a prop is far from an exact science and this is where the J-Prop shines. Ours was off one click from sizing but I tried two other clicks just for the heck of it because it is so easy...

Before our boat went in the water I marked my two potential pitches that were where we had calculated.

Mark Pitches With Black Paint Marker









Dive and Pull Pitch Adjuster Aft:









Rotate 1 Click and Release:









Pitch adjusted in less than 40 seconds while holding your breath...

Haul-out for a J-Prop pitch adjustment is not necessary unless you launched it in "boatyard lock-down mode".... Once it is spot on you can re-install the pitch adjustment lock when you haul out..


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## Melrna (Apr 6, 2004)

The beauty of resetting the pitch on this J prop was one of the reasons for selecting it in the first place, say over a Max Prop. However, resetting in the water while easy enough before the lock ring is placed can be dicy in poor visibility and cold water. The ease of maintenance is the other. So we are in agreement on this. I am just not getting the performance out of it as I guess you are. We are southbound right now on the ICW. We are only getting 6.2 vs 7.8 knots our normal cruising speed. We get full RPM's on the engine (3000) per Yanmar and J prop and the propeller is clean. 
When talking with Stan he finally admitted to me at the boat show about the lose of performance due to the flat blades of this particular propeller.


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## Don L (Aug 8, 2008)

I had a 3 blade MaxProp feathering prop on my last boat and have a 3 blade Flex-O-Fold folding prop on my current boat. On both boats I didn't have any lost of speed under power! The big difference to me is the the F-O-F prop seems a lot more efficient that the Maxprop (and I haven't been able to tell the difference between them in reverse and think that is just a wive's tale).

But to me a major PRO to getting a feathering or folding prop is so you don't have to listen the the shaft spinning when sailing!!!!!!


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## bobperry (Apr 29, 2011)

Four blade Max Prop is a great prop.

I have done a lot of prop testing, using the same boat. Very interesting experiments.

One thing all the props we tested had in common was the ability to drive the boat at hull speed. We did not have J Prop to test or a F-O-F. They were not available then.
Kiwiprop gets good reviews. I have a buddy who has one and he loves it. It's rather inexpensive.


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## Capt Len (Oct 9, 2011)

This thread reminded me that I still have a Max 17" 1 1/4 shaft 3 bld Nearly new but the lug in the hub is sheared off (drift wood) Apparently it's fixable in Seattle. Any one interested, make an offer.!!


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## jimrafford (Jan 7, 2011)

2nd the KIWI. Love ours. IFIRC it was about $1500. The other prop I was considering at the time was a Flexefold. That estimated out at $3700. Figured the KIWI was worth the gamble. Great prop.
Jim


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## Faster (Sep 13, 2005)

Capt Len said:


> This thread reminded me that I still have a Max 17" 1 1/4 shaft 3 bld Nearly new but the lug in the hub is sheared off (drift wood) Apparently it's fixable in Seattle. Any one interested, make an offer.!!


I bought our Max used, also 17' X 1.25 shaft.. but the shaft taper was different. For $400 PYI made me a new hub. Good quick service too!


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## MedSailor (Mar 30, 2008)

jimrafford said:


> 2nd the KIWI. Love ours. IFIRC it was about $1500. The other prop I was considering at the time was a Flexefold. That estimated out at $3700. Figured the KIWI was worth the gamble. Great prop.
> Jim


Any down sides? Loss of top end performance? Same or different rpm to reach hull speed?

Sent from my SAMSUNG-SGH-I537 using Tapatalk


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## Capt Len (Oct 9, 2011)

I was running a business so easy to absorb the expense of a Max and allowing my old gaffer the bonus of fabulous speed under sail was a no brainer But I pranged a big bronze prop (ice) in Tuk and was glad I could heat (tiger torch) and bang it back to perfect. while I hung from a 500 ton crane (connections at Dome) If off the beattin track (Like north of Lund)no way would I go for the delicate whirring thing.


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## Minnewaska (Feb 21, 2010)

I'm another fan of MaxProp. Service is great too. I had a nick out of a leading edge, so sent it back over the winter. While repaired, the entire prop looked brand new!

I'm sure we get some sort of sail speed advantage, but I can't say how much. I hate hearing the shaft spinning on a fix prop in neutral, especially when I go down below. I can't really tell if something is wrong, if it's always making a racket. 

It's also hard for me to say, if I lose speed under power. I don't feel like I do. I run about 60-70% of max rpm and get speed about a half to a full knot below hull speed at those power settings. Seems reasonable. Obviously, I could juice it up to 80%, but I don't think the fuel burn is worth it and these power setting push me along at around 8 kts. 

I believe Max Prop now also sells a prop, whose pitch is adjustable without disassembly.


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## bobperry (Apr 29, 2011)

Minn: Yes they do but I'm not sure if that feature is available on all models. We are using the five blade on the new Pacific Seacraft 63.


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## djodenda (Mar 4, 2006)

I like my 3-bladed Max Prop, which replaced my old 2 bladed fixed prop. Motoring performance is about the same. Took two tries to get the pitch right. Happy customer


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## fallard (Nov 30, 2009)

I'm happy with my 25 year old, 3-bladed MaxProp. I do a lot direction reversals waiting for 2 drawbridges between my dock and open water and it has never failed. The gearing is solid, although the blades are thin. Without cupping, the blades have to be less efficient going forward, but that is a two-edged sword, as the reverse thrust is incredible. Helps when maneuvering in tight quarters.

I once winched up a concrete block on its polypropylene line that wrapped on the prop. The engine stalled and I was left with all 3 blades ripped and dog-eared. PYI fixed it for somewhere in the $400+ range. Some years later, I had PYI rebuild the prop by "plating" the blades (that had pitted over the years) and recreating the original shape. PYI also tightened up the fit of the parts. That was more $$, but the result looked like a new prop for far less money than a replacement. 

Bottom line: The MaxProp is a great product and PYI provides incredible customer support--both over the phone and in their shop. Yes, I would recommend it to a friend.


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## Fstbttms (Feb 25, 2003)

Minnewaska said:


> I believe Max Prop now also sells a prop, whose pitch is adjustable without disassembly.


There are several Max Prop models (one of which has been available for quite a few years) that have external pitch adjustment controls.

That said, *any* model Max Prop can be installed or removed or lubricated or have its pitch adjusted while the boat is in the water. Never a need to haul for any of this.


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## Jeff_H (Feb 26, 2000)

Melrna said:


> What they don't tell you is the other side of the story: motoring. Most if not all folding propellers lose power, the ability to propel your boat as fast as your fixed propeller. How much is lost will depend type of boat.
> 
> Cruising Sailboats - Those sailors that are full-time/part-time cruising, and/or with heavy displacement boats and need all the performance they can get while motoring should consider not putting on a folding/feather propeller. Major power losses of up to 1-2 knots could result in putting on one of these propellers. With my J Prop I have seen losses of up to 2 knots.
> 
> ...


With all due respect, you may accurately be describing the behavior of the specific prop on your boat, but your conclusions are way too broad a generality which really do not seem to apply in all cases, or even in most cases. I believe that it was Max Prop who used to publish a detailed scientific comparison of their prop vs fixed props of equal thrusts at equal effective pitch. They claimed that they had lower blade drag when motoring and so were getting better fuel efficiency and requiring lower RPM's to obtain the same thrust.

That is similar to my experience with my boat which has an ancient Martec folding (not feathering) prop. When I bought the boat, there was a spare fixed prop that was supposedly the original prop that came with the boat. I had Martec recondition the old prop and so used the fixed propeller for a while. The fixed prop clearly had slightly but noticeably less speed at the same rpm and poorer ability in reverse. During the swap I noted that the folder had a larger blade area than the fixed which may be part of it. I did not run a precise fuel comparison but I would have to assume that the fixed propeller was using more fuel since it required more rpms to achieve the same speed through the water as the folder. This was especially noticeable on a day with big chop and wind on the nose.

Jeff


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## paul323 (Mar 13, 2010)

Melrna said:


> I am starting this thread for two reasons. My utter disappointment in my feathering propeller,* J Prop*, and "Buyer Beware" of performances gained and lost when putting on a folding/feathering propeller.....In summary, the pros of a folding/feathering propeller, less drag while sailing and better reverse performance when docking (no or little prop walk) Cons: loss of horsepower while motoring and expense.


I would be interested to hear how the issue was resolved - I hope it has been! I have the Max-prop (feathering). The guys at PYI could not have been more helpful. I have gained:
* 1+ knots speed increase under power (same RPM).
* Increased efficiency and reduced propwalk in reverse (difficult to quantify)
* 0.5kn+ more speed under sail. 
* Ability to sail in light airs.
* Actually won a beer can! 

My old gal is 32', around 13klbs dryweight.

I agree that props like the Max are very expensive, but I regard it as one of the better upgrades I have recently undertaken. My experience seems to have been reflected by all of the other posters. I am so sorry that your experience has been so poor - I am guessing that there must have been something wrong with the sizing, installation or adjustment. But don't write off the technology...


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## fallard (Nov 30, 2009)

Fstbttms said:


> There are several Max Prop models (one of which has been available for quite a few years) that have external pitch adjustment controls.
> 
> That said, *any* model Max Prop can be installed or removed or lubricated or have its pitch adjusted while the boat is in the water. Never a need to haul for any of this.


While it is true that you can install, remove, adjust my older 3 blade MaxProp in the water, PYI does not recommend this for the DIY types. We had to do this once and it took an hour and a half with SCUBA gear to reinstall mine. You'd better hope the water is warm enough to work without gloves when you replace those little cutoff cotter pins! Won't do this again.


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## bobperry (Apr 29, 2011)

There was ONE guy in Seattle who would adjust a Max Prop with the boat in the water. One guy.


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## Fstbttms (Feb 25, 2003)

fallard said:


> While it is true that you can install, remove, adjust my older 3 blade MaxProp in the water, PYI does not recommend this for the DIY types. We had to do this once and it took an hour and a half with SCUBA gear to reinstall mine. You'd better hope the water is warm enough to work without gloves when you replace those little cutoff cotter pins! Won't do this again.


I wasn't inferring that it should be done by anybody but a qualified diver, which PYI will happily recommend.


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## Fstbttms (Feb 25, 2003)

bobperry said:


> There was ONE guy in Seattle who would adjust a Max Prop with the boat in the water. One guy.


One guy could handle the amount of business we're talking about, I guarantee.


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## fallard (Nov 30, 2009)

Fstbttms said:


> I wasn't inferring that it should be done by anybody but a qualified diver, which PYI will happily recommend.


And PYI had NO recommended divers in my area. That's why we did it ourselves. It isn't brain surgery, but there are a lot of parts still subject to gravitational pull!


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## jimrafford (Jan 7, 2011)

MedSailor said:


> Any down sides? Loss of top end performance? Same or different rpm to reach hull speed?
> 
> Sent from my SAMSUNG-SGH-I537 using Tapatalk


Didn't notice any downsides. Rpm's and speed the same.
Plus sides. Prop walk in reverse pretty much went away and no loud clunk when you engage reverse.
Jim


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## Omatako (Sep 14, 2003)

So if you don't want the intricacies of a folding or feathering prop and a fixed-blade prop gives you too much drag but you still want the efficiency of the fixed blades, how about one of these - seems like a nice combination


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## MedSailor (Mar 30, 2008)

Omatako said:


> So if you don't want the intricacies of a folding or feathering prop and a fixed-blade prop gives you too much drag but you still want the efficiency of the fixed blades, how about one of these - seems like a nice combination


Looks cool, but I don't see either the avoidance of complexity or the retention of reliability there.

MedSailor


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## Omatako (Sep 14, 2003)

MedSailor said:


> Looks cool, but I don't see either the avoidance of complexity or the retention of reliability there.


There is actually very little complexity and the "machinery" is really quite simple. The "P" bracket with shaft and everything is a one-piece assembly, lifted/lowered by a simple hydraulic system and the inner shaft joins the outer shaft through a load bearing constant velocity joint (much the same as is used in the axle ends of any front wheel drive car). Importantly, the two shafts run in a straight line while the prop is deployed, thus avoiding any vibration or accelerated wear.


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## MedSailor (Mar 30, 2008)

Sounds cool. Would definitely avoid the snagging of lines and nets.


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## Capt Len (Oct 9, 2011)

Newfie dorrys have done that since engines were invented (sort of a long center board slot at the stern. )helps when hauling up a rocky beach.


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## sony2000 (Jan 30, 2013)

For under powered boats you can't beat Autoprop. It finds the maximum torgue for that RPM.


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## Jaramaz (Aug 9, 2013)

sony2000 said:


> For under powered boats you can't beat Autoprop. It finds the maximum torgue for that RPM.


Really? Care to explain how a prop finds the maximum torque at a given RPM?

Most sailboats are underpowered from the perspective of today's motorboat design. OTOH most boats having an engine is overpowered from the perspective of being able to drive the boat (in particular from a theoretical point of view, ie flat water ...). Thus the "underpowered" view doesn't say anything.

However, Autoprop is known. Works fine in some deployments - but of course not always. There are more important factors than "underpowered". Shaft angle is one ...

/J


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## SimonV (Jul 6, 2006)

I have had the KIWI prop for 7 years, If I get a new boat I will look at fitting a KIWI to it. The only down side is reverse......it is severe, I would like the manufacturers to fix this issue as it is the only negative. My perkins 4108 cant get past 1200 rpm in reverse. entering my slip and selecting reverse is like pulling on the hand brake.


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## sony2000 (Jan 30, 2013)

Really? Care to explain how a prop finds the maximum torque at a given RPM? 

I wish I could. But at the Club we have a cat ketch that is very underpowered. The owner is a shipwright.
This boat has worn all the props, without success. But with the Autoprop, it outperforms all the others.
"It outperforms all the others, in all aspects."
As a commercial pilot, the blade design is quite unusual. 
On sailboats I've seen props that were cast backwards, and sold with long production runs.


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## sony2000 (Jan 30, 2013)

Kiwi: The only down side is reverse......it is severe, YES


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