"Prop Options"

Prop Options

Someone started a new thread over at the E list @ Sailnet for info on props.
I have a photo of our Martec feathering two-blade from the haulout a couple months ago. Note that there is some angle to the blades, to hopefully shed lines. This prop has external adjustment for both forward and reverse. They can be sourced from dealers or directly from Martec. It has been in use since about 1996. Not cheap, but about $300 less than the Maxprop feathering prop, and their "Max" is not adjustable without taking it apart.
OTOH, the Martec can be adjusted in the water, if you have dive gear.

Hope this information is of some help.


Loren in PDX
Olson 34 #8

Good info about a 3-blade featherer

http://www.wbryant.com/StellaBoat/Projects/newprop/index.htm

Here is the latest set of pics from Wally's fine upgrade side. This shows good close-ups of a three blade Martec Autostream SS feathering prop installation.
As normal, Wally's notes are complete and helpful.
I still like my two blade bronze, after about a decade, FWIW.

I note that the grease fitting and adjustments for forward and reverse are just like mine.

Loren in PDX
Olson 34

I have an Autostream on my E39 that came with my boat. I'd recommend it highly. Although I probably would've hesitated buying it due to the cost, I am glad that the boat came with it. The original pitch set by the PO was off slightly. At the last haulout I adjusted the pitch - took about 30 seconds without removing the prop. I could probably do it underwater with just snorkel gear - it was that easy.

I'll show you mine...

This is the KiwiProp (New Zealand) that I just put on in April. As with the original 2 blade fixed Michigan, we're getting over 6 knots. However, max revs forward are a few hundred low, so I'm going to back off the adjustment screws (one per blade) a half turn when I can brave the 62 degree water for a few minutes with my snorkel on a calm day. Unlike most other props, the blades feather independently so laminar flow is optimal.

One drawback of the KiwiProp is you are over propped in reverse and they claim that reverse pitch is not adjustable. In max reverse we are at 1500 rpm instead of 2900 ! I'm looking into that now. The 3 protuding cones in the picture are the reverse stops which I may be able to replace with slightly fatter ones.

The greasy looking stuff on the prop is a voodoo mixture that I heard about of zinc oxide and castor oil. I'll be diving the hull frequently so I can clean up if the voodoo doesn't kick in for KOKOMO.

The Autostream looks like an excellent product (all stainless steel) and I would prefer it except for the price. The KiwiProp was $1300. I saw in a forum that the Autostream can be purchased from the actual manufacturer if you are in Australia for about $1000, but if you buy from Gori here it's $2500-3000.

bbboat said:

I have an Autostream on my E39 that came with my boat. I'd recommend it highly. Although I probably would've hesitated buying it due to the cost, I am glad that the boat came with it. The original pitch set by the PO was off slightly. At the last haulout I adjusted the pitch - took about 30 seconds without removing the prop. I could probably do it underwater with just snorkel gear - it was that easy.

Click to expand...

The Kiwi's interesting. Never heard of it before. One aspect of the Autostream I like is that the reverse pitch is user-adjustable, and reverse thrust is greatly improved. In fact, in the manual they warn you that your reverse performance is likely to be improved 10x over a fixed prop - guess they don't want you to accidentaly rev too highly and back into the dock!

FYI - I'd be curious to know how well that voodoo mixture works at keeping the growth off - I'm using Vaseline right now.

kiwi prop reverse

I tried an emergency stop from full speed ahead. It took between 1-2 boatlengths, so I feel that reverse thrust is adequate.

I do know that at only 1500 rpms we're not getting anywhere near full power out of the M25XP and that running full throttle reverse for long periods would not be good becasue of coking issues. Typically we only do full throttle reverse very briefly to set the anchor or pull it out.

He did a terrific job documenting the Autostream install. I actually wasn't aware of the prop shaft chopping issue on the fancy feathering props. The Kiwi Prop I installed just goes on over the standard tapered shaft where the Michigan sail prop came off -- no shaft cutting. You use a square drive to tighten it from the aft end and then there are a few allen screws to lock it in place.

Loren Beach said:

http://www.wbryant.com/StellaBoat/Projects/newprop/index.htm

Here is the latest set of pics from Wally's fine upgrade side. This shows good close-ups of a three blade Martec Autostream SS feathering prop installation.
As normal, Wally's notes are complete and helpful.
I still like my two blade bronze, after about a decade, FWIW.

I note that the grease fitting and adjustments for forward and reverse are just like mine.

Loren in PDX
Olson 34

Click to expand...

just fyi,

We purchased a Gori two blade folding prop, 11 1/2 " diameter and 8 degree pitch, that will be installed this weekend. My only concern, looking at the shaft, strut and rudder from the dock, is whether there will be enough clearance between the strut and the nut on the prop, but also whether there will be enough clearance between the rudder and the prop blades when they're folded. I presume there will be enough clearance, but the length of the prop, when folded, is 11". I guess I'll wait and see. I'll send photos when available.

By the way, I went with Gori over Martec because of the gearing on the blades, which is supposed to avoid one blade flopping open when under sail and is supposed to improve performance in both forward and reverse. Our current fixed two blade prop sucks in reverse, so it can't get too much worse.

Jim McCone
Voice of Reason E-32-2 Hull #134

Voodoo update

Earlier in this thread I mentioned a "voodoo" mixture of zinc oxide and castor oil. I read about it in another forum. Well by ten weeks (Early July), the engine rpms started dropping. I dove the prop last month and discovered about 1/2" of barnacles on the hub and inner blades (see my previous photo). After cleaning the rpms were fine again.

Of course I don't have a control for this experiment but suffice it to say that I don't believe in the voodoo mixture for Kokomo. Maybe Kokomo have bad jo-bu for prop anitfoul !

I'll be diving it again soon I guess. Just wish that low pressure snorkel I ordered would come in.

Installed Kiwi on my 38-200

I am VERY impressed with the prop. Due to the low weight (<10 lbs) of the composite blades, it is very smooth. The stoping/backing performance is exceptional as well, but I am a little over propped forward and reverse as previously noted is fixed. One thing I liked it I believe all the blades start from the same blank and are CNC machined reducing cost. Also, it allows a larger blade since they are custom to your application. I believe my prop is just shy of 17 inches in diameter. Each prop is serialized so you can purchase a replacement blade for ~100 that is based on the original CNC program. Not to discount the merits of the max and autoprop, they command a premium and are still in business hence they are obviously doing something right. I can say that I have absolutely no regrets about the Kiwi and the yard that installed my new engine were very impressed as well.

regards
shaun

down under is the down under prop

I'm very happy with the Kiwi for half the price of the other under water adjustable feathering props. Last month I dove the prop and made a slight adjustment to all three blades in a few minutes with three breaths of air. It was slightly overpropped. I also like the fact that the blades can easily be removed underwater for repainting. The original installation on the standard shaft taper was a breeze with the Kiwi design.

When I dove the prop barnacles were growing on the fat inner part of the blades only but scraped off easily.

I think the soft spot is the reverse performance. When it turns 1500 rpm versus 2800 max in forward I know I'm not getting to the sweet spot of the M25XP. It's adequate for anchoring and emergency stop in a few boat lengths from 6 knots but my only concern is running aground gunkholing. That's when you want full power reverse immediately.

That being said, after ten years of gunkholing experience is keeping me out of those groundng situations more so maybe full reverse power isn't such an issue for me.

From an engineering (or re-engineering) standpoint, I studied the Kiwi design. I see a way to reduce the reverse pitch and increase performance by milling the stops and increasing the size of the reversing cones. The same stops are used for forward and reverse, so the forward pitch adjusting screws would have to be cranked out some more to maintain the same forward pitch. Since the manufacturer hasn't offered this I am skeptical of the approach.

wurzner said:

I am VERY impressed with the prop. ...

regards
shaun

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'85 E35-3 Prop Size

I am considering replacement of orig prop. Power is orig (rebuilt) M-25. Calculations are done on pitch, but I do not have any documentation of measurement from center of prop shaft to hull to calculate max diameter. Could dive or haul, but would appreciate it if anyone on the thread could provide the measurement. Also, was there a standard prop fitted by Ericson? Or was this a buyer option?
Thanks
Dick Starr
E35-3 Yadin