[aeventyr60]

What are the handling differences between the 2 props? Moderate displacement boat, modified fin keel, spade hung rudder, powered by a Perkins 4108?
Prop walk to port?
With a velvet drive tranny, sail with gear in neutral or reverse?

 

[Ajax_MD]

I can only speak to the 2-blade Martec-

Yes, prop walk to port. Easily countered, once flow is built up over the rudder.
Very weak backing power.

As the pivot pins wear, sometimes a blade won't flip out when you put the engine in gear. A quick burst in reverse, then back to forward usually sorts it out. Do NOT throttle up with only one blade out or it'll knock the fillings out of your teeth. Potential engine mount and shaft log damage may result.

 

[jzk]

2 blade is better cruising efficiency. 3 blade is better power for acceleration/deceleration.

If I were going to replace my prop, it would be hands down for a 2 blade flexofold.

 

[aeventyr60]

I can only speak to the 2-blade Martec-

Yes, prop walk to port. Easily countered, once flow is built up over the rudder.
Very weak backing power.

As the pivot pins wear, sometimes a blade won't flip out when you put the engine in gear. A quick burst in reverse, then back to forward usually sorts it out. Do NOT throttle up with only one blade out or it'll knock the fillings out of your teeth. Potential engine mount and shaft log damage may result.

On dismantling the prop, what are the signs of wear on the pivot pin? I can guess, but what did your eyes tell you? Also, long split pin aft of the prop through shaft, looks like a weak link to me. Your thoughts?

 

[Fstbttms]

FYI (and maybe you already know this) but Martec doesn't make a 3-blade folder. Martec distributes the Slipstream 3-blade folder, but it is not a Martec product. Or maybe you were speaking about 3-blade folders in general and not specifically about Martec. :batter

 

[aeventyr60]

FYI (and maybe you already know this) but Martec doesn't make a 3-blade folder. Martec distributes the Slipstream 3-blade folder, but it is not a Martec product. Or maybe you were speaking about 3-blade folders in general and not specifically about Martec. :batter

I should have been more specific...a 2 blade folding martec versus an old school mickey mouse ears 3 blade fixed propeller. My bad.

 

[Ajax_MD]

On dismantling the prop, what are the signs of wear on the pivot pin? I can guess, but what did your eyes tell you? Also, long split pin aft of the prop through shaft, looks like a weak link to me. Your thoughts?

I've never heard of the long, split pin failing. (Doesn't mean it hasn't happened.)
Signs of wear are slop in the blades. That's all I can tell you.

 

[JimsCAL]

I have 25 year experience with Martec folderws on my last 2 boats. Some comments.

The wear Bubblehead mentioned is common. Slop in the blades is the indication. Martec will recondition the prop with a new oversized pin, rebalancing, etc. for a reasonable fee. I've done it twice and they do a great job. Just google their website for details.

I find the backing power OK. Not like a 3-blade fixed, but it works.

There are three cotter pins - two for holding the pivot pin in and one for locking the shaft nut. Never had one fail.

 

[Faster]

The other place they get 'sloppy' is in the cheeks that capture the blade roots.. The 'one-blade-open-shakes' are downright alarming the first time!!

For a non racer the smoothness and 'power' of a fixed 3 blade prop will always be better, but the drag significantly more. A good compromise would be a 3 blade Campbell Sailer Prop.

West by North Enterprises - Campbell Sailer

They offer other alternatives as well..

http://www.westbynorth.com/

 

[Ajax_MD]

When I grow up and earn enough money for a replacement, I'm going with a Kiwi Prop: Kiwiprop Home of the Kiwi feathering prop

 

[Fstbttms]

There are three cotter pins - two for holding the pivot pin in and one for locking the shaft nut. Never had one fail.

There should actually be four cotter pins. The nut should have two, one going in through each side with ends spread on the inside of the nut.

From the Martec web site:

Install (2) Monel cotter pins thru holes in hub; one from each side of the hub. Cut the cotters to fit and spread inside the nut.

install_eliptec.gif

 

[MedSailor]

My perkins 4.108 with a velvet drive tranny spun the other way and thus I prop walked to starboard in reverse.

If you have a left hand prop, you'll prop walk to starboard.

If you have a right hand prop, you'll prop walk to port.

MedSailor

 

[capta]

My perkins 4.108 with a velvet drive tranny spun the other way and thus I prop walked to starboard in reverse.

If you have a left hand prop, you'll prop walk to starboard.

If you have a right hand prop, you'll prop walk to port.

MedSailor

One boat I purchased had the prop turning the other way on a Velvet Drive as well. It wasn't until we'd burned out the trany that we realized that the PO had purchased the wrong prop, so he changed the shifter cables. Forward operation was running the trany in reverse, and Borg Warner tranies don't do well like that.
I'd be inclined to check the trany if your boat prop walks to starboard. Just a thought.