Flexofold Prop problems

[bertboyer]

We have an Olson 34 with a Flexofold feathering prop. Not sure what exact model, but I can ask the previous owner. The problem we are experiencing is that it goes into reverse well, but hesitates for many seconds before going into forward. Not a good thing when we are backing out with a current and another dock is just behind us leaving only 4-6 feet of room before we need to go into forward!

Loren referred us to a diver who took some nice video's of the prop. I am sharing that info in hopes that someone on the site can give us some guidance. Flexofold is responsive to our emails, but doesn't seem to have a clue as to what is wrong.

From the videos below, the Flexofold prop looked very clean and easy to open and close by hand. The gears also looked clean and not clogged with anything. The shaft seemed to easily turn clockwise and counterclockwise. This confirmed to me that there is not an issue with the transmission and the shaft turning. The linkage seemed fine and my view of the shaft turning from the engine view seems normal. Here is the first video of the diver checking out the prop.

In a second video, the diver put his go pro camera on a stick while someone was at the helm putting the gear in forward and reverse.

In the video, it is a bit hard for me to discern exactly what was happening when the gear was in forward or reverse, and what the prop was doing. It did seem like the prop was spinning and then a few times there was a cylindrical rush of water. That must have been when the gear finally engaged in forward. The bottom line is that the shaft linkage seems to be working as the shaft is spinning...but the prop is not opening up. It's unfortunately beyond my skill set to know why.

At least we know that the prop was not fouled with weeds or something, and that the transmission seems fine. The Flexofold company rep said that the prop is lubricated by water. I thought it might be worth our time to sit at the helm with the boat tied on securely and just put it in and out of forward and reverse gears several times to loosen whatever is stuck. Short of that, I can only think of a haul-out and possible prop replacement. Here is a blog on the flexofold prop: https://blog.flexofold.com/how-to-maintain-your-flexofold-folding-propeller?hs_amp=true

I'd appreciate any thoughts you might have. It seems some EY.o members have flexofold props and love them. I wonder if anyone has had a similar experience or knows what next steps to take.

We are out of town until October 28, but I will check email occasionally during our trip.

Thanks in advance for any help you may be able to offer!

Bert

 

[peaman]

The performance of the prop is affected both by centrifugal force (open when spinning) and hydrodynamic pressure (open or close depending on water flow direction and speed), while a conventional fixed prop isn't substantially affected by either. Observations made while tied to the dock won't tell the whole story. It seems clear that the issue is with the transitioning flow condition at the prop, which is affected by movement of the boat through the water. That being said, I don't have a clear explanation for a too-long hesitation in getting traction.

I wonder how aggressive you are with throttle after shifting into forward? Maybe after shifting, you just need to give a lot more throttle before reducing throttle once forward motion is detected or reverse motion is stopped.

This post agrees that "a bit more wellie" (throttle=boot=Wellington) may be needed.

 

[AK67]

I agree with Peaman. I have a Martec Eliptec Mark III folding prop, but yours seemed to operate as it should. More throttle makes sense = more centrifugal force to open faster and more fully. It would also seem to me that if you're in reverse, and then shift to forward then your sequence is: fight and stop aft momentum -> zero momentum -> gain forward momentum. And that may account for the delay you're experiencing? "More wellie" also counteracts the aftward momentum faster.

 

[bertboyer]

Thank you both for your thoughts. I'm not convinced this is the issue for a few reasons. Let me explain further.

First, this was not a problem for the previous owner, who had the boat in the same dock for 11 years, just a few slips away. In fact, the previous owner still races with us regularly and he now experiences the same issue when at the helm. This problem started to occur after the boat was on the hard for bottom painting, inspection, and a few minor repairs (none to the transmission).

When we back out of our slip, we are going in the same direction as the current, so very low reverse speed is needed. When we shift to neutral and then forward, we do give a lot more throttle, but often we experience no forward propulsion for several seconds... as the rear dock looms closer to the aft of our boat. Eventually, with only a foot or two to spare, we get forward propulsion, but the problem seems to be getting worse as it is slower to engage and we are getting more fearful of being pinned to the rear dock by the current. Note that one other Olson 34 and an Ericson 34 are on the same dock, one just two slips from us and they have the same prop, but no issue. They are also perplexed with our issue.

I still don't understand why we don't see immediate prop wash while being tied to the dock and putting the gear in forward with significant throttle. It can take several seconds or more recently, no prop wash until we try a second time.

While we are relatively new sailors, the previous owner sailed for 40+ years and he is also perplexed with the problem and it is not something he experienced in the 11 years he owned the vessel.

Hope this helps to clarify our situation. We welcome more thoughts from you and others.

Thank you!

 

[Frank Langer]

Is the cable adjusted correctly so the transmission goes completely into gear when you shift? If not, it could explain slow engagement.
Frank

 

[Prairie Schooner]

Sorry, no help on the propeller, Bert, but thanks for these videos. Especially the second one. Really fascinating to see the prop in action.
It looks like it isn't fully unfolding at first.
Do you have the typical Hurth transmission? This seems like just the behavior of ours. Good in reverse but it took X seconds to engage in forward. We have a solid prop. The transmission was way overfilled with fluid and it seems to be working better now that I have that right. Touch wood.

 

[Nick J]

This sounds like a transmission issue. Maybe this thread could help:

Hurth Transmission Woes

My Hurth HBW50 slips in forward gear, as I have described on other threads in the past. I am taking a long time getting it done, but planned to pull the trans & replace with the next bigger ZF10. I have the boat mostly apart to pull the trans, but a dockside friend with a powerboat (he crews on...

ericsonyachts.org

 

[bertboyer]

Is the cable adjusted correctly so the transmission goes completely into gear when you shift? If not, it could explain slow engagement.
Frank

Yes. It seems adjusted correctly and I can see the shaft spinning when in gear and spinning faster when more throttle is applied. Looks the same in fwd and Rev

 

[bertboyer]

This sounds like a transmission issue. Maybe this thread could help:

Hurth Transmission Woes

My Hurth HBW50 slips in forward gear, as I have described on other threads in the past. I am taking a long time getting it done, but planned to pull the trans & replace with the next bigger ZF10. I have the boat mostly apart to pull the trans, but a dockside friend with a powerboat (he crews on...

ericsonyachts.org

Thanks Jeff and Nick. It is a Hurth transmission. The transmission fluid was changed in the yard in January by a well respected yard and mechanic. I can check the fluid level when we return in a couple weeks. I'll also read the Hurth blog. Thanks for the lead.

 

[Prairie Schooner]

Thanks Jeff and Nick. It is a Hurth transmission. The transmission fluid was changed in the yard in January by a well respected yard and mechanic. I can check the fluid level when we return in a couple weeks. I'll also read the Hurth blog. Thanks for the lead.

Our transmission was (over)filled by a tech working with a respected marine diesel mechanic. Just sayin'.

 

[bertboyer]

This sounds like a transmission issue. Maybe this thread could help:

Hurth Transmission Woes

My Hurth HBW50 slips in forward gear, as I have described on other threads in the past. I am taking a long time getting it done, but planned to pull the trans & replace with the next bigger ZF10. I have the boat mostly apart to pull the trans, but a dockside friend with a powerboat (he crews on...

ericsonyachts.org

Thanks so much for this thread. Back in 2008, Rocinante33 said the following:

Symptoms include:
1. Backing out of slip, everything is great. As the boat slows, move the shifter to forward & apply throttle.....nothing happens (except the boat drifting toward other, very expensive vessels). Repeat the process 2 or more times and maybe a very soft "clunk" is heard, whereupon forward motion begins.

This is EXACTLY our experience! Even the soft clunk sound. Looks like we need to find a professional transmission mechanic as this repair is well outside my expertise.

 

[Loren Beach]

Some observations from up here in the cheap seats...
Read up on the mixed experiences boat owners have had with rebuilding the Hurth model 50, We opted not to - and that was a little part of the Concern List that factored into our repower, but that's just one data point.

And getting back to "the door we came in thru" the basic design of a folding prop has some baked-in geometry challenges with getting the blades to open reliably. I have a friend that found that it took a hard reverse throttle to get his to open, and this got real scary in a tight marina fairway. He converted to a feathering prop to solve the problem, and it did so.

On our boat I used a two blade feathering prop for a decade and found that the "right" internal grease was absolutely critical to allow the gears to function properly so the blades would reverse.
While we do regret the loss of sailing speed with the present fixed prop, the simplicity of it is appreciated. "Everything's a compromise" as the saying goes.
All the best.

 

[Loren Beach]

This problem started to occur after the boat was on the hard for bottom painting, inspection, and a few minor repairs (none to the transmission

Knowing that, over the decades, this transmission model has been problematic for many owners, this little sentence sorta makes me curious to know know what was done to it recently. Maybe not relevant, but I do wonder.
Perhaps best to move a previous Hurth 50 thread up to current status or start a new about the Hurth 50.

 

[bertboyer]

Knowing that, over the decades, this transmission model has been problematic for many owners, this little sentence sorta makes me curious to know know what was done to it recently. Maybe not relevant, but I do wonder.
Perhaps best to move a previous Hurth 50 thread up to current status or start a new about the Hurth 50.

Loren,
Thanks for continuing to think about this. Not sure what you mean about moving a thread up to current status. Are you suggesting I start a Hurth 50 thread? Apologies for my confusion...

 

[Loren Beach]

The easy way to move an existing thread into “current “ status is to add a Reply to it. This will put it at the top of the page again. I sometimes do this by adding “bump “ as a reply because the original thread topic has been raised again

 

[Prairie Schooner]

Bert,

In reference to Loren's suggestion, if I find a thread that seems to really connect with what I'm experiencing, I take up the conversation there to continue with already established input. It moves that thread to the front of the queue and is a way of concentrating the accumulated knowledge.

This thread also has some good discussion:

Hurth Transmission Oil [E35-3]

So I am to be condemned for the fact that we have owned our boat for three seasons, and I have not changed the transmission oil. This is due to two facts: 1. The amount of boat yoga to get to our drain plug is daunting, in fact I am not sure if I can reach it without taking the heat exchanger...

ericsonyachts.org

> In post #25 Grant @G Kiba speaks of switching to 30W oil and eliminating the slipping problem. If we continue to have problems with slipping, I'm going to try this before I move to replacing the transmission. He discusses this in a couple other threads, though I can't remember where.
In post #36 I link a great video that shows how these transmissions look inside and work.
In post #43 I link a bunch more threads on these transmissions.

In case you decide to go the replacement route, John @JSM replaced his with another model, with some discussion in these two threads:

New Transmission for 34-2 / M25xp

Picked up a new Twin Disc MG 340 along with a new damper plate this morning to replace my occasionally slipping Hurth HBW50 and will be attacking this project in the near future. Have been reading all I can find and the job seems like it should be fairly straight forward (yeah sure!) Has...

ericsonyachts.org

35-3 replacing HBW-50 with Twindisc need model details

My 1989 35-3 has a Universal M25XP mated to a HBW-50 transmission (that has failed). From reading all threads about this topic on this I am going with Twindisc tranmission to replace it (because it's cheap and good). But tried to figure out the exact model has been a challenge. I need to know...

ericsonyachts.org

I have a friend who successfully rebuilt the Hurth 50 in his Hinckley Pilot 35. But he's a brilliant mechanical engineer and industrial designer. I wouldn't hazard it myself.

J

 

[bertboyer]

Thank you Jeff.

It will take me some time to get through these threads....especially while on holiday in Italy. But I will start shortly.

Best,

Bert