Folding propellers

Ta!
I will definitely investigate this "feature" before making my final decision.
Damn! They, (kiwi feathering) seemed ideal.
I have a 3 blade fixed and cannot fit a folder in the space.

 

jonsailor,

could you tell more about this?
- what boat?
- shaft or saildrive? (or whatever)
- more info? 9 knts, average or some few tops? is the prop close to the surface at these high speeds?

I am rather interested in the Kiwi, your info is really bad news!
- did anyone contact Kiwi on this?

BR

/J

 

I still don't know the brand of my 2 bladed feathering prop but now that I've had the oppurtunity to use my (sail) boat more I've made the following observations. Bearing in mind this prop is old and the internal gears are probably quite worn and the blades a bit floppy.
1/I get more power astern the ahead.
2/ The blades don't reliably feather and sometimes the prop will spin when sailing fast.
3/ It CAN get bound up with weed and not funtion.
4/ Probably due to the wear but 98% of the time I cannot use full power ahead as I get dreadfull vibration but on a few rare occasions (either after motoring for some time or suddenly opening the throttle wide) I can run with full throttle and things will be amazingingly smooth. So clearly the blades are not opening evenly each time.
Due to cost I might have to consider a fixed blade prop when I get a replacement.
If I can ever find out the brand of prop I currently have fitted I'll post the message here.

Mychael

 

Mychael,

- folding or feathering?
- name usually stamped on the hub. Clean it thoroughly. Might also be on the inner side of the blades (have to de-mount)

1) some gearboxes actually have different gearing forward and reverse. Check your engine manual / data sheet. Some folding props has to be reversed slightly to open (and some other vv).

2) most folding props open during sailing if the gear is in idle/neutral. Put it in forward och reverse, and the spinning will stop. (fixed blades are of course even worse on this)

3) All props do attract weed. and anchor lines. and everything else

4) this vibration might be due to the prop, but more likely to the shaft bearings. When did you change last time? The last (most aft) bearing is often a cutlass bearing. should be replaced every ... depends on use, but still at least every 10 year.
It is a wellknown phenomenon that there are some critical revolutions, where there are resonance ( => vibrations), and above these there is again no resonance. (the resonance is actually periodic, usually one only notices the first). Your engine might be a bit tired from age, and then can only overcome the critical area in smooth wheater or similar.
- theories & speculations, of course.

- why do you want to replace your prop then?
(and to a fixed ... not good for sailing performance).

/J

 

Feathering, prop will pitch out to zero blade twist.
1/ No engine or prop date came with the boat. When boat was out of water last time prior to purchase tried to identify prop but no markings could be seen . Since have been advised it may be a Gori.

2/ Engine was serviced 6 months ago when I purchased the boat. I know shaft glands were replaced but not sure about the bearings.

3/ Engine is a bit tired, although runs smoothly at full power in neutral and starts okay. It does not smaoke very much but after 5 hrs continous running it will have used about 50% of it's oil. (going by dipstick marker).

4/ I know it's not the original engine for that boat so at some stage this (larger) motor was installed. I suspect it was a 2nd hand unit with some workable life left in it.

5/ Given the aformentioned engine change it may not even be the correct prop for the motor. Primarily I want to cure the vibration.

Mychael

 

If it is a Gori, then it is stamped at the hub. Probably paint and fouling and other niceties are covering the mark (it took me some time before I noticed the stamp on my own prop).
Then there is also a stamp stating prop size, as e.g. 16" x 12" (or just 16 12) and some letters like RH (means right handed, i.e. clockwise). The first number means diameter, the second pitch.

Gori is considered to be one of the best folding prop marks. They use to last long. They use to have cogs at the blade hub ends, which ensures a balanced opening / folding (if correct mounted).

Further, if your prop works, i.e. the engine is able to get to the max rev/min (see manual), and if the boat moves with acceptable speed forward and acceptable handling reversing, then there is no reason to change prop.


To the vibrations, then:

is your engine aligned with the shaft? Check! This can easyly be checked within fractions of mm, and that is the requirement as well. When a new engine is installed, then it often is aligned at installation - but this needs to be checked after some time as the engingen moves a bit in the cradle.
(look in your manual, or at the net, or find a general boat manual, like Nick Calders). This should be checked when the boat is in the water.

And then check the bearings. easy done, can the shaft be moved around a bit, or not. Can be done in water (with a snorkel).


And finally, to the engine: sorry to say, an engine should not consume 50% of motor oil during 5 hours .... no consumption at all, in fact. (I guess you do have some black smoke, look carefully. and what is the color of your motor oil after some few hours running? Black?).
This indicates some leakage between the furnance part of the eng and the "oil" part. Could be some few different issues, propose you consult a diesel mechanic on this (you might want to read a book on the subject as well? There are plenty).
It could be the engine that introduces the vibrations - if there is leakage in one cylinder, then then engine does not run even and smoothly.

Good Luck

/J

 

There is no tachometer (rev counter) so I cannot tell if motor achieve full power but feels as if it is revving quite fast.

Oil after change was still clean after first few hours of use. Naturally got progressivly darker with use.

I would say it has acceptable speed in forward and reverse (with the proviso) that to get "acceptable forward speed" I must endure considerable vibration.

The engine is a 2 cylinder Yanmar and was serviced by a Yanmar dealer.
Looking over the receipt, they replaced.
Drive belt,mixer exhaust and gasket,anode plugs,boat exhust hose, water pump impellor,bearings (not stated where),and the usual filters etc.
Checked, flex coupling and checked engine alighnment, repacked stuffing box.

The did an engine run-up and reported ok.

So that really only leaves the prop as the imbalance.

Mychael

 

You should have a look at www.g-prop.at
feather prop from stainless 316TI same price as kiwiprop from plastic.