Martec Folding Prop

Macgyro

Amazingly Still Afloat
Blogs Author

Very Subjective question here, but I just purchased a used Martec Elliptical folding prop that was beautifully refurbished at the factory. It fits perfectly on my 3/4" shaft (1970 Ericson 32 w/Atomic 4), but (during dry test fitting) as the blades extend, they hit the rudder and overlap the rudder about 1/2".

The advice from the Martec factory was to remove the shaft, have 1" taken off the front end, and then I should have plenty of clearance. The blades have lots of clearance folded and extended, it's just the transition that's troublesome.

The big reason for my propeller change is that the 3 blade fixed prop on the boat only let the engine get up to 1800 RPM and really bogged down the engine. I don't know the pitch, but I think it was too much for the Atomic 4. Another complaint with the three bladed fixed, is that the stern would travel 10' sideways for every foot backwards. The original two blade was sitting in a drawer in the boat, so I was going to put that on this winter and check it out until I saw the craigslist ad for this folding prop (12" x 6")

My question is: Is having a folding prop worth all the trouble of having the shaft shortened, or should I install the original two bladed 12" x 9" prop and sell the Martec? I don't race, but half a knot is half a knot, you know?

-Dean
 

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Alan Gomes

Sustaining Member

Very Subjective question here, but I just purchased a used Martec Elliptical folding prop that was beautifully refurbished at the factory. It fits perfectly on my 3/4" shaft (1970 Ericson 32 w/Atomic 4), but (during dry test fitting) as the blades extend, they hit the rudder and overlap the rudder about 1/2".

The advice from the Martec factory was to remove the shaft, have 1" taken off the front end, and then I should have plenty of clearance. The blades have lots of clearance folded and extended, it's just the transition that's troublesome.

The big reason for my propeller change is that the 3 blade fixed prop on the boat only let the engine get up to 1800 RPM and really bogged down the engine. I don't know the pitch, but I think it was too much for the Atomic 4. Another complaint with the three bladed fixed, is that the stern would travel 10' sideways for every foot backwards. The original two blade was sitting in a drawer in the boat, so I was going to put that on this winter and check it out until I saw the craigslist ad for this folding prop (12" x 6")

My question is: Is having a folding prop worth all the trouble of having the shaft shortened, or should I install the original two bladed 12" x 9" prop and sell the Martec? I don't race, but half a knot is half a knot, you know?

-Dean
Dean,
Based on your pictures, I'd say that it would be a good idea to shorten the shaft regardless. Ideally you want the forward end of the prop hub to be positioned no more than one shaft diameter aft of the strut. This is to prevent the shaft from whipping. Sometimes the geometry does not allow for this--such as, for example, when moving the prop forward would result in insufficient clearance between the blades and the bottom of the hull. But ideally, for a 3/4" shaft, you would want the forward end of that prop's hub to be no more than 3/4" from the strut.
 

supersailor

Contributing Partner
Definably the shaft is too long. I have the same general problem. My shaft needs to be shortened about 2" when I haul this year. Your prop would be good on my boat.
 

Phil MacFarlane

Member III
I agree with the others, your shaft is TOO LONG. I have a martec folder on my boat and I love it but... it will take some getting used to and probably won't help your reverse issue. In reverse it wants to close. You have to overcome this with high rpm. Also if you let barnacles grow on it, it could prevent it from opening evenly causing an imbalance wich would not be good. So, if you don't dive on the boat or have it dived on regularly it might not be a good idea. But for sailing its the best prop in my opinion.
 
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Mort Fligelman

Member III
Martec Prop

Dean:

I have posted on another Martec question some time back......but damned if I can remember the context....I Plead Ancient Mariner (senility).

I have had a Martec on every boat I have owned since 1970......I am sure that the 1/2 knot in moderate wind is correct......but in the super light stuff...no question that there is a difference, particularly from a 3 blade fixed.

My e35 3 came to me with a 3 blade fixed, and in light air it felt like a slug.....I put the Martec on, and maybe it was just mind over matter, but I really thought I felt a difference.

I certainly agree with the shortening of the shaft......at least with the torque of a diesel....and it would be my guess that the higher RPM of the Atomic 4 could cause the shaft to whip and create some problems.

As with all my posts......my opinion, and FWIW

Good Luck
 

markvone

Sustaining Member
Dean,

In the Chesapeake with it's light winds you will see the most benefit with the folding prop UNLESS you just don't sail when it's light. If you are like me and try and sail whenever you can, even in the lightest winds, the Martec will make a big difference. I wouldn't consider a solid prop on my boat for that reason. I don't find reverse to be a issue. I have never had the prop not open. Occasionally, I'll get only one blade to open which is immediately noticeable by the "thunk, thunk, thunk" noise and the vibration. I shift to neutral-reverse-neutral-forward and it opens.

The bigger issues to me are how rusty is the shaft coupling at the transmission, how hard will it be to remove the shaft and does the rudder have to be dropped? If you already need to work on the shaft seal or the cutlass bearing or you are thinking about a dripless shaft seal then do all of this at the same time.

Mark
 

Macgyro

Amazingly Still Afloat
Blogs Author
P.S.S replacement

Dean,

The bigger issues to me are how rusty is the shaft coupling at the transmission, how hard will it be to remove the shaft and does the rudder have to be dropped? If you already need to work on the shaft seal or the cutlass bearing or you are thinking about a dripless shaft seal then do all of this at the same time.

Mark

I actually have been thinking about doing a dripless shaft seal, but need a lot of other things more urgently. It looks like everyone agrees that regardless of my prop choice, the shaft should be shortened, so I'll probably see about sliding the shaft out. I know the coupling bolts are in good shape because I just had them out last year at the engine replacement, but I didn't remove the prop shaft coupling, so the set screws are in unknown condition. Hind-sight being 20/20, I should have removed the coupling (and a few other things) and cleaned it while the engine was out and I had room to reach back there.

With my estimated available time, if I have to drop the rudder, I'll stick with the fixed two blade on the too long shaft. If I can get the shaft out without removing the rudder, I'll try for the folding prop.

Thanks for the help!

Dean
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Why does the prop shaft have to be cut at the inside coupling end when it would be so much easier to cut it at the propeller end? There must be a good reason--can someone enlighten me?
Thanks,
Frank
 

Macgyro

Amazingly Still Afloat
Blogs Author
Prop Shaft


This end of the prop shaft looks a lot more complicated to re-create than the forward end. Although, I haven't seen the forward end yet, I hear that it's just a keyway and maybe some set screw divots without the taper. I wish it was so easy as to just grind off the back inch.

By the way, I have a bullet shaped zinc about a third of the way between the cutlass bearing and where the shaft exits the keel. Where is the best place to put the zinc (or more than one) to reduce any "whipping" or vibrations?

I didn't get out to the boat today :( so I'll have to look at removing the shaft next week.

-Dean
 

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Alan Gomes

Sustaining Member
This end of the prop shaft looks a lot more complicated to re-create than the forward end. Although, I haven't seen the forward end yet, I hear that it's just a keyway and maybe some set screw divots without the taper. I wish it was so easy as to just grind off the back inch.

By the way, I have a bullet shaped zinc about a third of the way between the cutlass bearing and where the shaft exits the keel. Where is the best place to put the zinc (or more than one) to reduce any "whipping" or vibrations?

I didn't get out to the boat today :( so I'll have to look at removing the shaft next week.

-Dean
Well, not only that, but even if you did decide to chop off some of the aft end of the shaft, you'd still have to remove it from the boat in order to have a machine shop "re-create" the taper and threads since that can't be done in situ. And that means getting it off the coupling in any event.

Re: the zinc placement--I wouldn't sweat that too much.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
I agree with the others that there is way too much unsupported shaft behind that cutlass.
Loren
 

markvone

Sustaining Member
Here's my setup - zinc location and shaft length

This is a 1 inch shaft. I have less than 1 inch between prop and strut. You can see where my two zincs were in the middle of the span between the strut and the hull. I don't have any vibration issues.

Mark
 

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Macgyro

Amazingly Still Afloat
Blogs Author
New Shaft, cutlass bearing, split coupling

Just thought I'd send an update for those who provided such great information. Installed the new propshaft, split coupling, folding prop, cutlass bearing, and re-stuffed the stuffing box with synthetic gore flax. The folding prop now clears the rudder at all angles, and the large gap is much narrower now. I didn't replace the entire stuffing box with a PSS, (which I really wanted to do) because I ran out of money a long time ago, so that'll have to wait....

Please let me know if you see anything that could be better. Your collective advice has proven valuable time and time again.

Thanks!
Dean


 

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