Someone to turn me some KiwiProp rollers in 316 please

P

Plevier

Well-Known Member
Joined
22 Aug 2008
Messages
3,594
Location
Brighton
Visit site
I have finally got all the dimensions to make some larger rollers for my KiwiProp to reduce the reverse pitch. Drawing attached.
These will reduce the pitch to about 19 degrees, a fraction more than my forward pitch, for an MD2020 with MS10L gearbox (ratios 2.35 fwd, 2.26 rev).
I'm looking for someone who could turn these for me - min qty 3 - preferably not too far away from me (Lewes near Brighton).
I have a piece of 25mm 316 bar that should be long enough.
Please PM me with contact details if you can help.

Anyone else interested in some?


View attachment 31628

Oops some dimension lines have disappeared, sorry, should be clear enough though!
 
vyv_cox said:
Is 316 the optimum material? I don't know the duty but 316 has a very low yield strength and could indent easily with a narrow applied force.
Click to expand...

It's lightly loaded, bears against the plastic blades and just has to rotate a bit when you go into reverse, not all the time, so I think it's OK.
The shouldered bolt it turns on is also 316. Not ideal but seems to work OK. (It's Kiwi's choice of material not mine.)
Advantage is that everything in the prop is 316 or plastic minimising corrosion. Oh there is a spiral spring too, don't know what that's made of, but it's enclosed and grease packed.
Thanks for the thought!
 
Last edited:
Let me know how the modifications work for you. I've been using a KiwiProp for 7 years but like you find the reverse pitch is too coarse. Unlike you I've been too idle to do anything about it! Did you discuss your idea with Vecta Marine or the manufacturers? They may be able to help.
 
Yes I have.
They say that there is no room for bigger rollers. I haven't been able to check as my boat is in the water but although I'm surprised I have to assume they are correct.
I'm trying to make shims to go on the blade roots. Much more difficult.
I'm afraid they steadfastly refuse to acknowledge that there is a problem and do anything about it themselves.
If this mod doesn't work the prop will be going on ebay, I can't live with it.

If the above seems contradictory - I have a spare blade I am using to try the fit of shims. Not an easy shape.
 
Last edited:
I don't know how many of the other people who now say they have problems with Kiwi reverse pitch have contacted Kiwi about it.
Kiwi treat me as though I'm inventing a problem that nobody else has and they show no interest in finding a solution (as they don't perceive a problem)
 
All those who cannot get the engine to rev in reverse - this means the mech is full of barnie critters. I had this in my first 2 seasons, noticed it started coming on toward the back end of the season.
The other indicator to this is the prop acts like a sideways paddle wheel in reverse, causing much prop walk, and virtually no reverse movement

For the last 5 seasons, I have completely crammed all of the internals with grease until it squeezes out of each surface. No further problems.
 
No FullCircle, that can be a problem but is not the answer for everyone. ("Paddle wheel" has happened to me when a roller was stuck and I know the difference; at WOT the engine stayed literally at idling speed and emitted clouds of soot.)
What I have is a specific problem where the gearbox has a higher ratio in reverse than forward. It affects at least some Volvos, some Yanmars and some Betas to my knowledge.
In extreme cases it can cause the engine to stall when reverse is selected.
In my particular case (VP MD2020D engine with the standard MS10 gearbox) , forward is 2.35:1 and needs 19 degrees pitch.
Reverse is 2.26:1 and the prop goes to 24 degrees pitch.
Look at the VP and Kiwi power curves and you will see why the engine can't rev and starts to overfuel and smoke.
The problem is there but less with SailDrives where ahead and reverse ratios are (usually) equal - 2.35:1 for current small VPs.
VP now (since 2002 I think) use ZF gearboxes. Previously they made their own and reverse was lower than forward allowing the Kiwi to give better astern than a standard fixed pitch prop.
Kiwi persist in saying on their web page "Volvo's will typically have 2.37:1 in ahead and 2.72:1 in astern in their most popular configuration." This is incorrect and has been for years.
They do admit "REVERSE RATIO: One cause of this can be that the reverse ratio of the gearbox is lower ( leading to higher shaft rpm in reverse than ahead ). This is an uncommon situation and is most likely to be found on Lombardini and some Westerbeke models. Sizing an optimum propeller for a reduction ratio of 2.6:1 in ahead will always lead to constraints on engine rpm in reverse when the reverse reduction ratio is say 2.18:1 simply due to the higher shaft speeds."
It's not as uncommon as they say!
 
Last edited:
Just a footnote.
I don't want to sound unduly critical of the prop or the people.
If I didn't like the prop I wouldn't be putting effort into trying to fix this problem.
Alan at Vecta and John in New Zealand are both taking an interest in my efforts and pointing out problems I might cause in other areas such as restricting the feathering, for which I am grateful.
Making a mod is turning out to be more difficult than one might initially think!
They are too busy with new products such as the 4 blader and some other general improvements to be able to put much effort into a problem affecting a small but I'm convinced increasing number of users and which has gradually emerged, I can understand that, limited resources have to be used on priorities.
Would I recommend the Kiwiprop? Yes, subject to careful checking of the compatibility of your gear ratios and engine power curves.
 
Last edited:
The point is my rollers don't stick now? That was part of my root cause, and on all the others I have 'advised' on. The mech is not fully engaged, making it a paddle wheel, which no amount of power is going to overcome.

If you want larger rollers to try, why not have some annular rings or collets turned up that fit over the current rollers. As they are inverse, you should be able to fix them for trials.

I believe that Kiwiprop's use of the word 'typically' is spot on. I have to admit I also think your gearbox ratio is 'rare'.
 
FullCircle said:
The point is my rollers don't stick now? That was part of my root cause, and on all the others I have 'advised' on. The mech is not fully engaged, making it a paddle wheel, which no amount of power is going to overcome.

If you want larger rollers to try, why not have some annular rings or collets turned up that fit over the current rollers. As they are inverse, you should be able to fix them for trials.

I believe that Kiwiprop's use of the word 'typically' is spot on. I have to admit I also think your gearbox ratio is 'rare'.
Click to expand...

Additional: If you always experienced this problem from the 1st application of reverse, why didn't you engage with them at that time?
 
FullCircle said:
I have to admit I also think your gearbox ratio is 'rare'.
Click to expand...

No, it's the standard one on the MD2020D - changed from the C version - and on the following D1-20 model as you can see if you look at VP's published spec sheets.
It's a standard Jeanneau factory fit not something odd.
With slightly different numbers the same applies to the 2010, 2030, 2040, D1-30 and D2-40. In all cases reverse is higher than forward, conflicting with the higher pitch.
The problem is less severe with the D range because they all rev slower than the MD series.
This relates to the inline drive. The box with the angled output shaft is different but much less common.
 
Last edited:
FullCircle said:
Additional: If you always experienced this problem from the 1st application of reverse, why didn't you engage with them at that time?
Click to expand...

I bought it used from someone who had initially had it on a Yanmar on which it was fine but he then re-engined with a Beta on which it was unsatisfactory because of its reverse ratio.
I spoke to Vecta before buying. They assured me in good faith that it would be fine with my engine/gearbox.
When problems became apparent we pursued various red herrings. It took some time for me to be certain what was the real problem as the change of configuration by VP was not well known.
So Vecta/Kiwi are not responsible for supplying this prop and I can't just reject it. I am grateful for the interest they are taking, they could wash their hands of it.
 
Had the same problem with reverse on two different yachts. On the latest I was going to shim the blades to reduce the pitch but decided to go with a conventional folder in the end.
 
You must log in or register to reply here.

Share this page

Top