Flex-O-Fold Propellers vs Kiwi

[Amurruman]

KiwiProp North American agent here. Some good feedback on this thread, but thought I would offer some possible clarification.
IF your new KiwiProp is stalling your engine right from the start, you have to recognize the difference between a symptom and a problem. We very specifically set the props up based on the HP, max rpm and reduction ratio of your boat. As someone mentioned, we are very diligent about confirming and cross checking that information to make sure it makes sense. IF you tell us your 20 year old diesel has 50hp but it is only putting out 40hp because of a faulty injector, carboned up exhaust, clogged fuel filters, etc. etc. then it will likely motor in forward fine but not reach max rpm as it is supposed to. In reverse, it might stall.
You could decide to treat the symptom and put your old fixed prop on that didn't give you any reverse thrust and might have been underpropped since day one, or you can treat the problem and have your engine refreshed.
There are some inexpensive work arounds to keep the Kiwiprop on and treat the symptom and defer more expensive options like rebuilds or repowering, but keep in mind the KiwiProp is just exposing the problem, not creating it.

IF after a year or two of use you start to experience stalling in reverse that is absolutely a completely separate maintenance issue, and you need to get grease into the hub and work it back and forth until you are sure it is not binding anywhere, then put some more grease in just to be sure!
There are now thousands of KiwiProps out there for over 15 years. Virtually all of them are being installed and maintained by the owners since we sell primarily direct from the factory. A small percentage have reversing issues that are almost always related to a lack of regular greasing. The prop will actually give you some warning before you have a major problem- an initial puff of black smoke when backing up. its not hard to grease, even underwater, and we ship a grease fitting with every prop.

[belizesailor]

Recently started my first cruising season with Kiwi Props...wow...what a difference under sail ! I've been dragging those old fixed blades around for way too long. Appear to have gained about a knot under sail. I don't have specific data to compare against (like polars with the fixed blades on), but the difference is very noticeable.

Under power ahead performance is about the same. In reverse, very much over propped, but effective...just took a little getting used to.

It would be interesting to swap on a pair of Flex-O-Folds and compare. They claim potential increased performance ahead under power versus fixed props in some of their testing. I find that hard to reconcile, but sure would be a bonus.

(Hey Flex-o-Fold...are you reading!)

[belizesailor]

Hmmm...gonna have to adjust my anchor setting technique to being overpropped in reverse too...snatched the hook out today while just trying to gently coax it a little deeper in difficult holding.

[sailcruiser]

I've been reading threads on props most of this afternoon. This thread has a lot of great info. I have narrowed down my search based on budget etc to a kiwi or a 3 blade FoF.

A few questions:

1. I have an old Volvo and saildrive: 35 hp max rpm is 2500 with a 1.66:1 reduction. I back out of a tight spot pretty regularly and have concerns regarding the reports of stalling I have read about. I did see the info about greasing everything but it seems 23 pitch in reverse is a bit much. Your opinions?

2. The lack of an anode scares me being in fresh water. Can an anode be present with a kiwi? Otherwise my drive may become an aluminum anode and that isn't a good plan as far as I'm concerned. If not what is usually done?

Right now either of these will help sailing performance by removing the 5 gallon bucket I'm dragging around. I lost a fixed prop last year and am not keen to repeat that fiasco.

Thanks,
SC


Sent from my iPad using Cruisers Sailing Forum

[mikereed100]

I have not had a problem with stalling with my 30 hp Nanni's, but they are sometimes not powerful enough to overcome the spring tension on the Kiwi's in reverse causing horrible noise and vibration and very little if any thrust. Taking most of the spring tension out of the props by rotating the hub mostly alleviated this problem. The tension is there to help persuade the blades to feather, but the new blade design does a good job of this on it's own. On the occasions that they still bind in reverse, I simply 'tap' the transmission into forward for a second, which rotates the blades, then put it in reverse. The next time I dive on the boat I may remove all of the tension.

[belizesailor]

Originally Posted by sailcruiser

I've been reading threads on props most of this afternoon. This thread has a lot of great info. I have narrowed down my search based on budget etc to a kiwi or a 3 blade FoF.

A few questions:

1. I have an old Volvo and saildrive: 35 hp max rpm is 2500 with a 1.66:1 reduction. I back out of a tight spot pretty regularly and have concerns regarding the reports of stalling I have read about. I did see the info about greasing everything but it seems 23 pitch in reverse is a bit much. Your opinions?

2. The lack of an anode scares me being in fresh water. Can an anode be present with a kiwi? Otherwise my drive may become an aluminum anode and that isn't a good plan as far as I'm concerned. If not what is usually done?

Right now either of these will help sailing performance by removing the 5 gallon bucket I'm dragging around. I lost a fixed prop last year and am not keen to repeat that fiasco.

Thanks,
SC


Sent from my iPad using Cruisers Sailing Forum

The stalling problem is relatviely uncommon I think. Kiwi offered to take mine back if they didn't work for me. No stalling problems for me (Vovlo MD2020s). WAY over proped in reverse, but no stall. Does smoke if I forget and apply too much throttle.

The standard zinc fits on my drives with the Kiwi props installed.

[belizesailor]

Originally Posted by mikereed100

I have not had a problem with stalling with my 30 hp Nanni's, but they are sometimes not powerful enough to overcome the spring tension on the Kiwi's in reverse causing horrible noise and vibration and very little if any thrust. Taking most of the spring tension out of the props by rotating the hub mostly alleviated this problem. The tension is there to help persuade the blades to feather, but the new blade design does a good job of this on it's own. On the occasions that they still bind in reverse, I simply 'tap' the transmission into forward for a second, which rotates the blades, then put it in reverse. The next time I dive on the boat I may remove all of the tension.

I sometimes get a bit of vibration in idle reverse, but a few more RPMs for just a moment resolves the problem.

[geoleo]

I had a Kiwi on y 35ketch. It caught pot lines and eventually bent a prop blade shaft-- they aren't sturdy like my current MAXPROP>

[belizesailor]

Originally Posted by georgetheleo

I had a Kiwi on y 35ketch. It caught pot lines and eventually bent a prop blade shaft-- they aren't sturdy like my current MAXPROP>

Ive rarely heard of any physical failures. Anyone else?

[belizesailor]

Originally Posted by Amurruman

...

You could decide to treat the symptom and put your old fixed prop on that didn't give you any reverse thrust and might have been underpropped since day one, or you can treat the problem and have your engine refreshed.
There are some inexpensive work arounds to keep the Kiwiprop on and treat the symptom and defer more expensive options like rebuilds or repowering, but keep in mind the KiwiProp is just exposing the problem, not creating it.

....

Had that experience this cruising season. Started getting some black smoke on port engine even in slow forward. Removed Kiwi Prop and put old fixed back on...smoke much less. Found no problem w the Kiwi prop. The Kiwis, even in forward, are more aggressive than my old fixed blades. I think they just revealed that I need some injector/injector pump maintenance (which I already knew was way overdue).

Swapping in the water was easy. My props are only about 2' underwater so no SCUBA necessary. Anchored in 8' of pure white sand so if I dropped anything it should be easy to find...fortunately nothing dropped.

[Sailingcouple13]

just put Kiwis on our cat hope to be back in the water next week. Upgrading from two blade fixed, looking forward to trying them out.

Sent from my SM-G900P using Cruisers Sailing Forum mobile app

[sailcruiser]

I ended up ordering the kiwi and have it installed. It definitely puts strain on my engine in reverse and needs a little extra throttle. My fixed prop needed no extra throttle in reverse. With the kiwi at idle the engine knocks and sounds very unhappy. I haven't had it out for speed tests yet but I think this one pushes me even faster at idle speed than my old 15" fixed. They recommended a larger prop thinking I was under propped. I may hit 4 knots in flat water now at idle with a 7.1 it hull speed.


SC

[malbert73]

Having had a variprop (feathering 4 blade) on my old boat and a flexofold (folding 3 blade) on my current, I really think feathering props are inferior to flexofold except in reverse. Forward is more powerful with curved shaped blades on folding prop, and it presents slightly less drag under sail I think. best is folded I don't have to worry about snagging lines.

Yes, sl anemic in reverse, remedied by more throttle.


Sent from my iPad using Cruisers Sailing Forum