Kiwiprop woes!

davethedog

davethedog

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Hello all,

Picked up our Moody 376 today and noticed that there is a problem in astern, in that the engine will not rev very much and appears under a lot of load, but not much revs! So , after much looking at the internet (including YBW) it is looking very likely that there is an issue with the Kiwi folding prop we have fitted to the boat not operating correctly.

So, a few questions as thinking of having the boat hauled out and a standard prop fitted to alleviate this issue, and allow us to at least use the boat for the rest of this year etc

1. Any ideas what prop I would need for a Moody 376, with a Thornycroft T98 engine (50hp) with the following reduction gears: forward = 1.89:1, astern = 1.179:1?
2. Where is the best place to purchase a prop for our boat at short notice?
3. Am assuming a prop can not be changed in the water, therefore bout will have to be lifted out?
4. How difficult to change a prop or best to pay someone to do it?

Thanks

Dave
 
Your prop isnnt greased UN the body and that means reverse us not working. Bet you can't get more than 2000 recs and the boat just goes sideways not backwards. You need to do this at the start of each season using the Mobil grease fro m vecta marine the kiwi dealers.
Do not give I have had mine for 11 years now.
 
It's usually what FullCircle says but on this occasion I'm sure there is more to it.
The KiwiProp is always at maximum pitch - I think it's 24 deg - in astern.
In forward it will be a lower pitch, typically 19-22 deg.
This is OK in the great majority of cases where the boat's reverse gear has a higher reduction ratio than forward. You can also get away with it when they are equal as with (most) saildrives.
There are a few cases where this is not so. I had one with a ZF gearbox on a VP engine, and an acquaintance had it with a Beta engine, I don't know what gearbox.
You also have this situation, to a pretty extreme level if the figures you have given are correct - that is a huge difference in ratios.
The KiwiProp will in this case behave as you say it does and will not be satisfactory.
Kiwi and Vecta know this limitation but don't like to admit it.
There is a makeshift cure for lower power drives, it worked on my 18HP, but I don't think it would work with your amount of power, it would destroy the reversing rollers, or with your extreme difference in ratios.
It's a good product in most cases but it does not suit all installations.

I can't answer your other questions, but the first things you must know accurately before you can get a different prop are your shaft diameter, taper angle and length of taper (or diameter at small end of taper). If you don't already have that info then it's a lift out and remove the Kiwi to measure. If you don't know what that involves and haven't previously dealt with separating taper joints then I suggest you get some competent help.
 
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Plevier said:
It's usually what FullCircle says but on this occasion I'm sure there is more to it.
The KiwiProp is always at maximum pitch - I think it's 24 deg - in astern.
In forward it will be a lower pitch, typically 19-22 deg.
This is OK in the great majority of cases where the boat's reverse gear has a higher reduction ratio than forward. You can also get away with it when they are equal as with (most) saildrives.
There are a few cases where this is not so. I had one with a ZF gearbox on a VP engine, and an acquaintance had it with a Beta engine, I don't know what gearbox.
You also have this situation, to a pretty extreme level if the figures you have given are correct - that is a huge difference in ratios.
The KiwiProp will in this case behave as you say it does and will not be satisfactory.
Kiwi and Vecta know this limitation but don't like to admit it.
There is a makeshift cure for lower power drives, it worked on my 18HP, but I don't think it would work with your amount of power, it would destroy the reversing rollers, or with your extreme difference in ratios.
It's a good product in most cases but it does not suit all installations.

I can't answer your other questions, but the first things you must know accurately before you can get a different prop are your shaft diameter, taper angle and length of taper (or diameter at small end of taper). If you don't already have that info then it's a lift out and remove the Kiwi to measure. If you don't know what that involves and haven't previously dealt with separating taper joints then I suggest you get some competent help.
Click to expand...

Assuming your boat was correctly quoted when it's Kiwiprop was ordered?
I had a similar problem last season. I discovered (using an optical RPM meter) that my engine RPM was lower then specified in the normal Yanmar manual. If you don't have the correct RPM (gearbox-ratio wise) for your prop it cannot deploy properly in reverse, Mine was about 180 RPM low, compared to the panel RPM. Easily fixed.
I strongly suggest you do the recommended winter greasing as well, since it is easy and works. Even if you take off the blades and clean the surfaces it is not remotely difficult. The performance uplift with a feathering prop is considerable - so investing some time in maintenance is worth the effort.
Meantime, cut down to minimum all battery load - electrics etc before engaging reverse. Or consider uping the basic idle RPM by ? 200 RPM?
 
First thing to do is to check that you can get full revs in forward to ensure the engine is running to maximum and that the prop blades are correctly pitched. As suggested earlier the weakness of the Kiwi is first the steep pitch in reverse which gives good stopping power, but poor speed in reverse, and the second is the lack of precision in setting the blades because of lack of lubrication. It could be that just lubricating the prop in accordance with the instructions will at least enable it to work correctly and you learn to live with the reverse characteristics.

If you do want a new prop then www.lakesterngear.co.uk in Poole is a good source. Expect they will recommend a 3 blade of around 15-16" diameter and 10" pitch. Shaft size is 1 1/4", but check. However, best to give them full details of your boat and engine so that they can work out size. A standard 3 blade prop will be about £300+VAT and you will need a nut as the Kiwi has a different nut.

If this boat is a keeper then suggest you invest in a Featherstream 3 blade from Darglow in Wareham. Other 376 owners (such as graham376 who posts here) have fitted one, and well worth the investment in terms of improved motoring performance and better speed under sail. have
 
Thanks for the replies and just want to use the bloody boat!

I never knew there was that much to it ref the props, and was hoping that we could just order a prop online and then get the boat lifted out and the prop fitted, then put back in.

The boat is a keeper for us, so a better designed and more durable folding prop may be an option, however aware they cost a lot more and to be honest at present I don't want to spend that as we've spent enough on the boat already and not used her!

Regards

Dave
 
Right, just going through the kiwi prop paperwork and have the following info ref the M376 shaft:

Shaft dia: 1.25"
Length of taper: 3.12"
Dia at end of taper: 0.990"
Thread is 0.75" BSW
Length of thread: 0.87"
Keyway: .313" (5/16")

So, wheres the best place to order a suitable prop at short notice!
 
My pal has also had problems with his Kiwiprop on his Colvic Countess 33. It has never given him the speed he got from his old prop and last month he hauled out and found the had lost a blade. Not very impressed.
 
davethedog said:
Right, just going through the kiwi prop paperwork and have the following info ref the M376 shaft:

Shaft dia: 1.25"
Length of taper: 3.12"
Dia at end of taper: 0.990"
Thread is 0.75" BSW
Length of thread: 0.87"
Keyway: .313" (5/16")

So, wheres the best place to order a suitable prop at short notice!
Click to expand...

Hmmm... Props don't come bored "off the shelf" they will be machined to fit your shaft, so "short notice" is basically no chance... It will be quicker, as you have to lift out to sort out the Kiwi
 
davethedog said:
Ok, where is the best place for me to get a normal prop from please?
Click to expand...

Steel Developments
Darglow
Silette Sonic

Flexofold make the best propellers IMO. I've had Gori and corroded two of those away. I've had Kiwiprop which stalled our engine in reverse, it wasn't low enough drag for racing either.
 
Very happy with my Kiwi for 5 years or so. As Mr Full Circle says, your woes will almost certainly be solved by a dob of grease. There are 5 points on mine that need a squirt of grease. MUCH cheaper than a new prop .......
 
Further to my previous post.
I'm not familiar with the Thorneycroft engine but it looks very big for your boat (to me).
If it has lots of torque at low revs, you MIGHT find you can live with the Kiwi at least for a while by only using very low revs astern. At the expense of limiting the sustained thrust available, it will avoid the engine struggling - and probably producing copious black smoke - trying to respond to a big throttle opening, and the coarse pitch will give you a good initial bite for a moment or two when you select astern.
If you are in a spacious marina and don't need to use astern much this may work, but be warned, the day you need lots of sustained reverse thrust, it won't be there. Worth experimenting though, using throttle much more gently. However at idle it may cause the engine to stall.

A good point of the Featherstream for your case is that the astern pitch can be set finer than the forward pitch, which is what you need.
I have a Flexofold now, with a saildrive with equal forward and astern ratios. Going astern you have to use a lot more throttle than forward and the thrust is much less because - like all folders - the blades don't open fully. This characteristic could also help cope with your unusual gear ratios. I would talk to Darglow for advice (they make the Featherstream and also support the Flexofold although they aren't official distributors.)

Whoever you talk to, make sure they take note of your gear ratios.
 
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I'm not sure where you sail Dave but I would just dry out on a beach or tie-up alongside, whip off the prop and grease it and put it back. Should take 30 minutes so you have plenty of time between tides.

I'm in the Med and can't dry out but I have a saildrive cat and the props have no taper and are very easy to remove and are not far below the surface so I could change mine at sea if I wanted to.

Richard
 
Davethedog, it must be apparent from the above that the fastest solution isn't going to be a new, fixed prop off the shelf. http://www.vectamarine.com/
Call Vecta and ask them, they have a strong interest in keeping you happy. Then call a good marine engineer, get the boat lifted and watch the engineer while he sorts it. It really is the fastest way to get to play with your new toy!
 
If you insist, I would use Sillette Sonic.

HOW TO ORDER

If you know exactly what you require then send an e-mail to sales@sillette.co.uk
fax: +44 (0) 20 8330 9014 - tel: +44 (0) 20 8337 7543.
Make sure you enclose your payment, detail as follows and advise method of transport.
 
Thanks for the replies and have decided I want a 'normal' prop now, just got to get round to getting one sorted out now.
 
Well, I had a look at the prop today and it turned OK and the blades appeared to twist, but still not happy with the thing!





Decided I would rather have a reverse gear that I can actually depend on, and then may try this prop again in a year or so?
 
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