Autoprop ?

[nhschneider]

I installed an H6 Autoprop on my 1984 Contest 48 in the spring of 1999. There were several things that prompted me to chose this model: The first being the article in Practical Sailor, which ranked the Autoprop as amongst the best compromise between fixed and feathering props. The second were the claims of increased cruising speed from the same engine RPMs. Also, our boat had a terrible ‘prop walk’ towards starboard in reverse – we had provided hours of entertainment to those watching us try to dock the boat up and down the west coast of North America.

The Autoprop did indeed increase our cruising speed. With our fixed blade prop at 2,400 RPM, we’d make about 6 knots. With the Autoprop at the same RPMs, we’d do 7.5 knots, a significant increase.

However, we did not experience any improvement in our ability to back up straight. The boat walks to starboard badly so we’re still providing the entertainment our dock mates love.

In April of this year, while anchored off of Manzanillo, I removed the Autoprop and replaced it with my original fixed blade prop. This is why:

The Autoprop requires annual maintenance and this cannot be done in the water. Either the boat has to be hauled or the prop removed. We discovered this the hard way once when we had a boat full of guests and one of the blades had ‘frozen’ in the reverse position, making forward progress very slow regardless of the RPMs. I had a diver remove the prop and after overhauling the prop and reinstalling it, Rutea moved as she had in the past.

A word about overhauling the Autoprop: It’s a relatively simple process that requires no special tools or skills. The only measurement the manufacturer specifies is the torque setting on the spanner nut that retains the blades. I did not use a torque wrench while rebuilding my Autoprop instead I just monitored the effort it required to turn the blade as I tightened the nut. I assumed that there should be zero free-play and that the nut should be tight yet the blade must be able to spin freely. This seemed to work fine plus I was able to approximate the torque setting specified.

The parts needed to overhaul the Autoprop are readily available from Autoprop or you can get most of the parts from any local bearing supply house. I say most of the parts as I was unable to locate the lip seals from anywhere other than from Autoprop. These seals don’t have anything unique to their appearance, in fact, appear to be surprisingly inadequate for the job they have to do. However, at $50.00 apiece, there must be something special about them but what it is escapes me. I was able to purchase the bearings for about $10.00 each and there’s two bearings per blade; one lip seal per blade. In the course of owning the Autoprop for 10 years, I overhauled it twice, averaging about 300 hours of motoring per year. The last time I overhauled it was during a haul-out in February of 2008.

In February of 2009, my wife and I took Rutea on a 4-month cruise to Mexico. While anchored off of Manzanillo, I dove the prop and found one blade to be very loose. I removed the prop and disassembled the loose blade. I found that the tab washer that locks the spanner nut had broken. The inside tab that indexes the washer to the stud had broken off, allowing the spanner nut to loosen. It was only a matter of time before the blade fell off altogether. I stowed the Autoprop in the bilge and reinstalled my original fixed-blade prop.

In all fairness to Autoprop, the propeller was due for service. However, the design that allows this small, inexpensive yet absolutely critical part (the tab washer that’s obviously prone to failure) that is required to retain the blades on the hub, is poor engineering. I feel that there must be a more positive method for locking the spanner nut – a cotter pin, a set screw or something that won’t fail as easily as the tab washer.

I had a conversation with someone from Autoprop where I asked if they were aware of any blades being lost. They said they were. This further supports my theory that while the Autoprop is a very clever concept, there are refinements required to it’s manufacture before the product is suitable for installation on a cruising sailboat.

Furthermore, according to a Segeln Magazine test http://www.propelspecialisten.dk/dow..._test_2008.pdf the Autoprop created almost as much drag while sailing as did a non-rotating fixed blade prop. It also shows that the thrust in both forward and reverse is amongst the best of any prop.

After extensive research, I have chosen a Gori 3-blade prop.

Fair winds and calm seas.

[cfarrar]

We used an Autoprop on our Nonsuch 30 for over 12 years and never experienced a maintenance problem. We now use a Maxprop on our Sabre 426. Here's my assessment: the Maxprop cteates a little less drag when faired, according to Practical Sailor and others, so it makes sense for a performance-oriented sailboat. However, the Autoprop is a better performing prop under power, especially while motor sailing or in waves. It's sort of like using a constant speed governor, the way it moderates the RPM changes by adjusting pitch with changes in boat speed and loading.

Yes, the Autoprop requires periodic overhaul, but so does a Maxprop, which also requires waterproof grease inside the gear assembly in order to function properly. The bottom line is you don't want to leave on an extended cruise without doing the appropriate maintenance.

I don't know about the Segeln Magazine test referenced in the previous post. The Autoprop may not be as slippery as a Maxprop or Gori, but I'm confident that anyone who replaces a fixed-blade prop with an Autoprop will realize a significant decrease in drag. See Practical Sailor, etc.

In conclusion, I would never consider a fixed-blade prop, because I like to sail fast. I have no experience with the Gori 3-blade folding, though I've heard good things. I believe the Maxprop has a slight advantage over the Autoprop while sailing, and the Autoprop a slight advantage while powering. Take your choice based on how you use your boat.

[j.g.evans]

My complaint with Autoprop is customer service. I lost a blade and despite several promises from Brunton to contact me, they never did. I now know my prop was part of a recall that I never heard about. A local dealer quoted a repair about equal to buying a feathering Autostream. I bought the Autostream for another boat and it is good.
As far as performanc goes I was not impressed. I did very careful speed versus engine RPM measurements in calm water. The response was linear until I reached the hull speed limit. It was just like my fixed 2B prop except it had the equivalen of 2" more pitch which was not desireable. I expected the auto adjust to produce a concave shape, i.e. more thrust and speed at low RPM.

[j.g.evans]

For any happy Autoprop owner, I have the 5H416 Autoprop missing 1 blade. This is for a 1" shaft. I also have a machined, bronze, adapter that replaces the Autoprop zinc and allows the use of a standard 1" shaft zinc. Anyone wanting this for spare parts for a price exceeding the scrap metal value should contact me.

[kellyp08]

Here's a story, perhaps of some help in this discussion. I had a 3 blade Max Prop on my 50' Hinckley. While going into Matinicus fighting against a 3 knot tidal current in a pea soup fog I noted that we were making only 1.5 knots SOG on the GPS. Normally we make 7.5 to 8 Knots under power. Next morning we were able to make only 4.5 knots tops under power (120hp Ford Lehman at 1800 rpms) over to Monhegan, Boothbay and back to SW Harbor where we sent a diver down who noted that the prop wasn't feathering. We hauled the boat and pulled the prop. Inspection showed that the internal cam had sheared off and fortunately the prop had jammed in a position that allowed us to make way forward. We called pYacht (the distibutor of MaxProp) who insisted that they never had this problem with these props but when they inspected mine admitted that there was a casting fault and replaced it with a new one. I, right or wrong, re-installed the fixed 3-blade prop. The downside of the fixed 3-blade under sail is free-wheeling with the hydraulic (Paragon) transmission and drag if a shaft brake is used. I was wondering if anyone else had a similar problem with MaxProp. I'd like to go back to the feathering prop as perhaps my experience is as unusual as pYacht claimed.

[paulrack]

I have a Max prop on my L34, works really well and has not given no trouble. I am not sure how old it is, but probably at least 14 years.

[Elie]

To answer Kelly08 , I had the same experience with my previous boat equiped with an Maxprop. While arriving at a busy service dock, I tryied to stop my 37 ft boat by reversing the prop. Nothing happened and to my dismay I hit a boat bow pulpit, with little damage by pure luck. Not funny. I had the boat out and find that the prop was blocked with the blades perpendicular to the shaft. The reason: A bad installation from the seller of the propeller. Normaly these events must be seen as accidents, and I think the occurence of these mishapes is in direct proprotion with the complexicity of this equipement. I fixed this installation problem and never had any other probleme with it. In my opinion, Autoprop props are heavy, and therefore require a very stable shaft, well aligned to perform and a well balanced prop to avoid any vibration. I had my Autoprop blades wheighted(over 2kg each) and had them slightly grounded (5 gr and 12 gr removed!) so they balance perfectly.

[Tidetracker]

I've been using an Autoprop for the past 13 years, on two boats, and have been extremely satisfied. The newer one, bought in 2005, is a better design than the one we bought in 1996. I like the efficiency while motoring, the auto-pitching attribute, and the relatively low drag while sailing (obviously not as low as some other designs, but certainly a lot better than a fixed pitch prop). The best attribute: absolutely NO propwalk in reverse. The worst disadvantage: due to the way the prop works, getting going from a standing start, or doing close manouvers, requires a more agressive use of the throttle, than do other designs.

EDITED TO ADD: I'm new to this forum, and this thread, so please excuse me if I'm repeating things already discussed... The Autoprop underwent a major redesign at some point before 2005; I know this because the one I installed on my Jeanneau was dramatically different than the one I had on my Catalina. The older design indeed had the infamous 'tab washers' that apparently failed at times and resulted in lost blades... the newer design has proper setscrews.

[Paul_Carroll]

Should anyone be so inclined, there is a used AutoProp H5-460 (18 inch) for sale in the Annapolis Craig's List.

[totako]

Hi!

I have a Contest 40S (1993). Do any of you have any information on what kind of an Autoprop would fit this boat? The boat has been fitted with a normal three-blade propeller by the previous owner. Im interested in replacing the current propeller with an Autoprop. I would be most grateful for any and all information regarding what propeller would best fit the Contest 40S.

Thanks, Tom.

[dkall]

Find someone who has a Contest 40S and an Autoprop. If you contact Autoprop, make sure they give you one for YOUR BOAT and YOUR ENGINE. My issue was the only seemed to care about the engine and if the prop would fit in the apperature. Once they remedied the situation then it all seems ok.

[Pete the Cat]

As a delivery skipper, I delivered a boat with an Autoprop and really did not like it. The "auto adjusting" feature seemed to make the boat hard to run at slower speeds even at idle--kept having to take it out of gear to maneuver in tight spots---pain in the butt. The engine would, like the other poster on this thread, only reach half its rated rpm at full throttle. I do not want this guy's diesel repair bills in the future. My experience tells me that a full feathering, pitch adjustable in the water, prop--preferably of stainless rather than soft bronze (ever met someone who hit something hard with their Max prop?--met some folks in Panama looking for someone to repair theirs) is what I have used for a decade with good results.

[squarerigger]

My boat had an autoprop when I purchased it six years ago and it was probably on there for two or three years before I bought it. Its worked without problems so far, but that's only been for about 600 hours. I plan to replace it with a fixed prop, perhaps a Campbell, (or even the three blade I carry as a spare) the insant it begins to look or sound suspicious. I love the concept of reduced drag, but I simply dont see the increase in performamce significant though it is, a worthwhile trade off for the complexity.

For what its worth, Neil I think you may have misread the graph in the article you posted. As I read it, the drag for the autoprop is about 20% of the fixed blade locked and 10% of the same fixed blade if allowed to freewheel. The autoprop does produce more drag than any of the other movable blade props.

Ray

[chala]

Originally Posted by Pete the Cat

The engine would, like the other poster on this thread, only reach half its rated rpm at full throttle. I do not want this guy's diesel repair bills in the future.

Could you give more detail on this statement.

[Pete the Cat]

Running a diesel at full throttle when it is only able to make half its rated RPM would mean to me that it is lugging and not able to cleanly burn the fuel that is being supplied to it--probably spewing black smoke, building up carbon and generally stressing the engine. I think that most diesel mechanics will suggest that diesels need to be run primarily around 80% of max RPM at cruising speed (not max boat speed) and hit max boat speed in quiet water at max engine RPM. I have only rebuilt a couple diesels personally, but this information is consistent with Dave Gerr's recommendations in his book on propellers. The Yanmar folks would not certify for warranty an engine I recently installed until the prop was pitched to meet this standard (be capable of attaining full RPM close to max boat speed).