New Prop Opinions - folding/feathering

[Letterkenny]

I currently have a fixed 3 blade prop on my Jeanneau powered by a Yanmar 3YM20 and am looking to replace it for (obviously) the sail performance increase as well as trying to get better cruise speed performance while under engine. I’ve read the article from about 2009 comparing them all but that didn’t touch on cruise speed performance other than saying a couple props saw a 300-400 RPM drop.

The three candidates are the flexofold 3 blade, the Autoprop, and the maxprop. I’ve heard of great speed increases on the Autoprop which is where I am leaning but sounds like that may have the most maintenance (but doesn’t seem like much?). Any opinions here or delivery captains that have used these and comments on performance in gear and reverse?

[HankOnthewater]

I just went though this process in replacing my nearly 30 yo max prop (due to crack in boss).
I really wanted an autoprop, as the specs showed advantages in motorsailing, speed under power, but......
- it was more expensive
- a more complicated setup
- no one could say for sure I could use a prop shaft alternator if I needed to, and it looked to me one could not

In the end I went with a max prop again, as that one can be locked-in to run my shaft alternator, rarely use it though, but with a new setup (removing the standard alternator) will get used more often.

[AiniA]

Have a look at
https://www.yachtingmonthly.com/gear...ler-test-29807

[ItDepends]

I have had the unusual experience of having delivered identical boats one with a Maxprop, and the other with an Autoprop.

Unless something is quite wrong with your current setup you will not see any real increase in top speed. In fact, if anything, actually a bit lower. When the engine is at full throttle, any properly sized prop will be transmitting all the shaft power to the water. At full throttle, a properly sized fixed prop is always going to be the most efficient choice.

What the Autoprop promises is that it can more fully load the engine at LESS than full throttle, which other props do not do. In theory, you will reach you normal cruising speed at a lower engine RPM, and the lower RPM requires less fuel becasue of lower friction losses.

I saw very little difference in performance. I did not monitor fuel burn, so can not comment on any changes there. In close quarters maneuvering, I found the Autoprop to have a bit of "lag" between pushing the throttle forward, and actually getting thrust. Not a huge difference, and not anything dangerous, but obvious. These boats have very little propwalk, so that wasn't a place to notice a difference.

If you have a hydraulic transmission you will need a shaft brake with the Autoprop, or it WILL spin while you sail. If you want to run a shaft alternator, they DO most certainly work with Autoprops.

If you do a lot of motorsailing, then the Autoprop might be the tool for you. I rarely motorsail, and increasing efficiency for the tiny number of hours I DO motorsail just doesn't come close to justifying the expense.

Be hardnosed about this. How many gallons of fuel do you burn in a year? What kind of efficiency increase would you have to see to justify the extra cost? Is that increase reasonable to expect?

[George_SD]

I've recently replaced 2 blade fixed for 2 blade folding
- not any faster
- may need a few more RPMs to reach the same speed
- slower to get going, especially in reverse (but totally manageable)
- you can hear it open up - CLACK!
- no more vibration from disturbed water flow across a 2 blade prop

Ease of install, simplicity of design, price, minimal maintenance requirements were important factors for me. Ended up with Eliche Radice. Otherwise would have gone with MaxProp probably.

[Jim Cate]

Do remember that Max Props (and all conventional feathering props) have lower efficiency than either Autoprop or Flex o Fold due to MP's flat, zero twist blade shape. This means that it will take a bit more horsepower developed by the engine to achieve the same thrust and this results in some loss of fuel economy at a given speed.

The test results have shown that the FOF folding three blade outperforms most other props, including fixed three blades... rather astonishing IMO.

Jim

[MicHughV]

I'm a big fan of the Max prop.

I was led to getting this, as my engine transmission was hydraulic, and once the engine was off, the gearbox could not be locked, and the sound of a whirling propellor is enough to make a saint grab a beer....or two....

I love it. It's a sturdy, well built item, and you can set the pitch yourself. Maxprop will give you recommended diameter and pitch settings for your particular boat and engine, but you can alter the pitch yourself if not happy with the performance.
Max prop has lots of experience with different boats, engines, transmission ratio's, etc.
and their recommended dia. and pitch settings are usually spot on.

Early models ( like mine) required the prop housing to be opened to set or reset the pitch, but the newer models can be reset without going thru' this trouble from the outside.

Max prop, besides selling new props, also sells "reconditioned" props, at about half the price of a new one. Mine was a "reconditioned" prop. When it arrived, I could not discern a single item of wear and tear. It looked brand new to me. Just call 'em and ask about reconditioned props.

Off course, the prop can be configured for either LH or RH rotation.

Max prop increases the prop blade area to compensate for lack of blade twist. Mine provided plenty of oomph.

Off course, in reverse, you get the same oomph as going forward, making backing out of slip a cinch.

I opted for the 2 blade model, as I could feather the prop behind the keel for the least possible drag. I would do this when racing the boat, ie, would dive overboard.

It has performed flawlessly.

There is simply no question, that it will improve boat speed. I can't speak for other props, but Max prop has certainly delivered the goods.

[s/v Jedi]

I recommend MaxProp as well. I have seen many boats replacing the bearings in Autoprop every year and one had even thrown a blade.

MaxProp is proven robust. I changed the pitch on mine to one point higher for motorsailing.

[Letterkenny]

Originally Posted by AiniA

Have a look at
https://www.yachtingmonthly.com/gear...ler-test-29807

Yes this is what I was referencing and was surprised to see the flexofold so high. Just wanted more references or differences under motor.

[Letterkenny]

Originally Posted by ItDepends

I have had the unusual experience of having delivered identical boats one with a Maxprop, and the other with an Autoprop.

Unless something is quite wrong with your current setup you will not see any real increase in top speed. In fact, if anything, actually a bit lower. When the engine is at full throttle, any properly sized prop will be transmitting all the shaft power to the water. At full throttle, a properly sized fixed prop is always going to be the most efficient choice.

What the Autoprop promises is that it can more fully load the engine at LESS than full throttle, which other props do not do. In theory, you will reach you normal cruising speed at a lower engine RPM, and the lower RPM requires less fuel becasue of lower friction losses.

I saw very little difference in performance. I did not monitor fuel burn, so can not comment on any changes there. In close quarters maneuvering, I found the Autoprop to have a bit of "lag" between pushing the throttle forward, and actually getting thrust. Not a huge difference, and not anything dangerous, but obvious. These boats have very little propwalk, so that wasn't a place to notice a difference.

If you have a hydraulic transmission you will need a shaft brake with the Autoprop, or it WILL spin while you sail. If you want to run a shaft alternator, they DO most certainly work with Autoprops.

If you do a lot of motorsailing, then the Autoprop might be the tool for you. I rarely motorsail, and increasing efficiency for the tiny number of hours I DO motorsail just doesn't come close to justifying the expense.

Be hardnosed about this. How many gallons of fuel do you burn in a year? What kind of efficiency increase would you have to see to justify the extra cost? Is that increase reasonable to expect?

Fuel efficiency isn’t a concern. It’s more so being able to have a higher cruise speed (e.g 6-6.5 knots instead of 5.5-6). It’s beneficial when doing overnights beating into the wind and current. Wish I could sail without a timeline but I cannot.

[Davidasailor]

We switched from a fixed 3 blade to a Flex-o-fold 3 blade on our 3YM30 about 5 years ago and have been completely satisfied.

Under sail we are generally at least 0.4 kt faster, especially at low wind speed. Also the fixed prop was causing lots of turbulence in front of our rudder, causing it to stall and round up if we weren’t careful about sail trim in higher winds. With the FOF we don’t have to worry about that nearly as much.

Under power we are at least the same speed as we were with the fixed prop, maybe a hair faster. We cruise pretty close to hull speed anyway. If you are motoring at 75% throttle and close to hull speed don’t expect huge speed increases from a new prop. You’re just at the limit for your boat. If you’re well below hull speed with your current prop you might be under propped or have something else going on. I’m not a believer in props that give the same speed at lower RPM. Seems that’s just lugging the engine unnecessarily.

The FOF is zero maintenance and still works like the day we installed it. Just replace the anode yearly like a regular prop.

Reverse is the one place the FOF doesn’t shine. At idle in reverse the FOF generates nearly 0 thrust. It takes about 1200 RMPs to slow the boat down as we approach our dock, instead of 800 with the fixed prop. But 1200 for a normal docking still leaves lots of headroom if there’s a need for any kind of more sudden stop.

[rbk]

Originally Posted by Letterkenny

I currently have a fixed 3 blade prop on my Jeanneau powered by a Yanmar 3YM20 and am looking to replace it for (obviously) the sail performance increase as well as trying to get better cruise speed performance while under engine. I’ve read the article from about 2009 comparing them all but that didn’t touch on cruise speed performance other than saying a couple props saw a 300-400 RPM drop.

The three candidates are the flexofold 3 blade, the Autoprop, and the maxprop. I’ve heard of great speed increases on the Autoprop which is where I am leaning but sounds like that may have the most maintenance (but doesn’t seem like much?). Any opinions here or delivery captains that have used these and comments on performance in gear and reverse?

Or go with a better fixed prop as another option: https://westbynorth.com/campbell-sailer/

[fstbttms]

"Autoprop- We hardly ever throw blades!"

[Loredo]

I had a Maxprop on my previous boat which I then replaced with an Autoprop. I'm not interested in a thrown blades, maintenance, yada yada yada war...
The facts about the Autoprop I can report are:
1) 30% less fuel used compared to the MaxP for same boat speed.

2) 400 Rpm less to get the boat to the same speed.
3) Way more powerful in reverse with almost no prop walk.

4) Maintenance is easy, once a year grease it. Maybe 20 minutes in all.
5) NO vibration / wear on the cutless bearing like with the Maxprop.
6) Both props are sensible to growth on them.

Autoprop recommends "overhaul" of the prop after 1000 Hours. Means, new bearings, seals, races... At 950 hours I overhauled mine (Simple if one is a good DIYer.), only to find out that it was wasted time and boat bucks.
There was nothing out of specs or had play or was worn. Since the prop was already apart, I changed out everything and kept the old parts as spares.BTW most parts do not need to be bought from Autoprop saving several dimes.
My still somewhat new to me boat has a four blade Flexofold.
I hate the non existing reverse thrust and the ridiculous propwalk it has.

When time comes, I'll go back to the Autoprop in a heartbeat.

On edit,
I forgot to mention the motor sailing thing with the Autoprop! Lull day, mainsail + genoa doing 2-3 kn... Turn on the engine, set it to 1000 R's and enjoy the show. 7-8 very effortless knots. I know, it sounds crazy but witnessed /done it a lot. The continuous pitch adjusting thing in all evidence works.


PS on yet another boat I lost a Maxprop and I know a few other sailors with the same problem. All props were professionally installed...

[s/v Jedi]

Originally Posted by Loredo

I had a Maxprop on my previous boat which I then replaced with an Autoprop. I'm not interested in a thrown blades, maintenance, yada yada yada war...
The facts about the Autoprop I can report are:
1) 30% less fuel used compared to the MaxP for same boat speed.

2) 400 Rpm less to get the boat to the same speed.
3) Way more powerful in reverse with almost no prop walk.

4) Maintenance is easy, once a year grease it. Maybe 20 minutes in all.
5) NO vibration / wear on the cutless bearing like with the Maxprop.
6) Both props are sensible to growth on them.

Autoprop recommends "overhaul" of the prop after 1000 Hours. Means, new bearings, seals, races... At 950 hours I overhauled mine (Simple if one is a good DIYer.), only to find out that it was wasted time and boat bucks.
There was nothing out of specs or had play or was worn. Since the prop was already apart, I changed out everything and kept the old parts as spares.BTW most parts do not need to be bought from Autoprop saving several dimes.
My still somewhat new to me boat has a four blade Flexofold.
I hate the non existing reverse thrust and the ridiculous propwalk it has.

When time comes, I'll go back to the Autoprop in a heartbeat.

On edit,
I forgot to mention the motor sailing thing with the Autoprop! Lull day, mainsail + genoa doing 2-3 kn... Turn on the engine, set it to 1000 R's and enjoy the show. 7-8 very effortless knots. I know, it sounds crazy but witnessed /done it a lot. The continuous pitch adjusting thing in all evidence works.


PS on yet another boat I lost a Maxprop and I know a few other sailors with the same problem. All props were professionally installed...

Please provide citations for your “fact” of 30% less fuel used. Facts are always documented; without supporting documentation it’s just personal opinion.

Edit: same for reverse thrust. All I can find shows that Maxprop has much more reverse thrust than any other prop.