On Oct 16, 4:29 am, "Dennis Pogson"
wrote:
Frogwatch wrote:
Anybody have experience with these? I am about to replace my fixed 3
bladed prop on my 8.5M S2. This looks like a potentially good
candidate replacement because they have already figured out which prop
works for a given boat and because they say they can put a larger prop
on with their "Extendo" system.
I am a little worried about the plastic of this prop not being able to
take my aggressive barnacle removal method. Is it easy enough to
remove that re-painting it every so-often works?
My old bronze prop has succumbed to corrosion and many impacts with
oyster beds and with a Laser mast in the water.

Now, one of the advantages of a 2 blade prop is that you can align it
with the keel for lower drag. How does one do this? Do you simply
mark the prop shaft inside the boat and then rotate it till your mark
is in the right place? This really seems like a PITA considering the
gawdawful engine installation on most boats. Even on my boat it
requires removing an engine panel and peering down into a dark space.
Is there any other system? Would the prop left in neutral auto-rotate
to the lowest drag position (I have never had a two blade prop so I
dont know) and stay?
Could I attach a magnet to the shaft so that it engages a magnetic
reed switch (non-contact) to tell me when it is in correct position?
Can you get it in correct position by "bumping" the start switch?

Ever heard of a thing called paint? You can even mark a prop shaft with it.
I won't charge for this piece of wisdom as I learned it about fifty years
ago. (and the piant is still there!) You could easily fit a small glass
spyhole in the cockpit floor. However, some sailors would argue that
allowing the shaft to rotate in neutral causes less drag than locking it in
the upright position, particularly on a modern fin/skeg design.

Dennis.

Dennis.

I appreciate y'alls advice, especially tsmwebb and Jere Lull. For
those who suggest a folding/feathering prop, I do not consider this to
really be an option due to the extreme fouling conditions I
encounter. A friend who works in a boat yard says most he sees are
too fouled to work around here. Cost is another issue for a boat that
is 27 yrs old.
tsmwebb points out that the flow is rarely directly fore and aft and I
admit this had never occurred to me, however, is he correct? If he is
correct, I would not expect a 3 bladed prop to cause much loss of
sailing speed.
As far as using paint and a sight glass as Pogson suggests, this was
my initial idea but drilling a hole in my cockpit floor for the sight
seems sacriligeous. I could easily rig up the magnet and reed switch
I described. However, how easy is it to stop a prop in a given
position unless you rotatre the shaft by hand? Can you "bump" it with
the starter to a given position? I cannot believe that most sailors
take off their engine cover to peer down at the prop shaft whenever
they sail to align the prop with the keel.