Folding prop replacement? Suggestions.

Another vote for the Kiwi. I'm nearing the end of my first season, and to date I've been very pleased with it. I get the sailing benefit referred to by others, and the reverse thrust at low revs is quite remarkable. Like FullCircle I get a lower speed / rpm curve in forward than with my old prop, but I don't see this as necessarily a problem. The Kiwi is finer pitched (in forward) than the old fixed job, so less fuel should be used at a given rpm than before, and at the end of the day it's knots against l/hr that really matters. The other advantage of the finer pitch is lower speed at tickover ahead - good for manoevering. I still can't get above 2500 rpm in forward gear, however, so I'll probably reduce the pitch a little more this winter. The engine is rated at 3200 rpm and achieves this easily in neutral. (I tried as an experiment last weekend seeing what full speed astern would do and max rpm was 1500!)
 
Thalassa,
I've heard someone at our local marina report problems with reverse with the Kiwi.
He said everything was fine until one day he selected reverse to stop the boat as he entered his berth and he could not get the revs to rise, it was as if the blades had locked in the sailing position and would not pitch for reverse.
He dived in to check and everything seemed OK but it has happened more than once.
He thinks it may be something to do with selecting reverse too quickly after being in forward.

He was told that he could return the prop for investigation and could have his money back if they found a problem but he would have to pay for the lift-out.

Is this a common fault and is it why you are having to have your reversing mechanism modified.
 
Wow. A few really full replies.

I fitted a KIWI earlier in the year - 3 blade, 18.5 inch at 23 degrees pitch, which is about as big as they go (I think). Had a problem with ingress of something that caused the mechanism to jam. Returned it to the supplier (forgotten the name - senior moment) in Pewsey and got a new one. No question that the UK supplier has integrity and is a delight to deal with.

The prop has increased our sailing speed by about a knot. The boat is much more lively and sails much much better.

The boat does a decent 6 knots at 2500 rpm in a moderate sea, which it would never do before. It does use more fuel at that speed (3 ltr/hour) but I think that's to be expected since I do use the power rather more. Previously I would have got 5 dropping to 4 after hitting a wave.

As has been observed by others, performance astern is startling with a real risk of getting waves in the cockpit. /forums/images/graemlins/smile.gif
 
Bonny,

i'm aware of the problems with 350 KIWI's produced last winter. I mentioned this in an earlier thread on KIWI's, but got blasted by a chap from Vectamarine that I was telling porkies. The local importer has written to all his customers that the problem could arise, and to be aware that one could have no reverse occasionally. I think he did excellent service to warn his customers, as a few weeks later I tried to enter a busy harbour in a force 6, and found the prop to be stuck. Luckily, I had part of a sail up and managed to get out of trouble. Changing from fwd to reverse and back at high RPM loosened the prop for a short while. I'm now firmly stuck in harbour, as I'm not fond of insurance claims.
Apparently, a ring in the mechanism was made in SS, replacing an earlier bronze type, because of corrosion worries. The binding in salt water of two SS rings sliding upon each other is a not universally know effect. The modification would consist of adding a Teflon ring.
Otherwise, I'm generally pleased with the prop, have no qualms about the plastic blades, having dried the boat out twice on hard sand. Not yet used to the hollow sound in the lower power band, and a bit mystified why Fullcircle has reduced or no propwalk, as I found otherwise, and see no technical reason for this. In reverse, the blades go to the highest pitch. Higher pitch = more propwalk. All IMHO, of course, every setup is different.
 
If your boat is correctly proped with a fixed prop you will not improve on ahead ability as the blades are correctly shaped for this - its just that astern the same blades are inefficient.

A feathering prop has flat blades that if pitched correctly will almost be as good as a fixed prop. Astern though the efficiency is drastically improved over shaped fixed blades going in the wrong direction!

The ability to alter pitch from outside prop I consider important as then yopu can fine tune your prop to your own hull/engine configerations as I believe there is still a small bit of the black art about sizing a propellor.

In my own case I want to increase ahead pitch so that engine does not quite reach maximum revs (slightly overproped) and went for a 4 blade (i think only variprop do 4 blades) as with 75hp I considered it would be smoother.

Very satisfied so far and cheaper than the Darglow equivalent Maxiprop but not as cheap as a Kiwi (size for size).
 
I'm considering getting feathering prop. Can't use Kiwi (only up to 55HP). I'd heard that Autoprop bearings tend to have a "short life". Has anyone had problems in this area? I'm looking seriously at Maxprop which I'd heard was better. Unfortunately it's all anecdotal...
 
Paul, I've had an Austral Slipstream (previously called 'the gear' I think) for about 20 years. The first 15 yrs it had very few horsepower behind it, so didn't give it any stress. It works very well, goes into reverse straight away and it's geared so the blades open together every time. It's available in 1" shaft sizes. They're in Sydney. I have no connection etc, just a happy customer.
http://www.australpropeller.com.au/ Austral propellers website
 
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