Proper size and pitch prop for 74 C&C33 MkI

[kwalters]

Just bought the boat and I am trying to confirm the proper size and pitch prop. I have some documents that came with the boat that look like the C&C original design specs that describe the boat as coming from the factory with:

30HP A4 with 2:1 reduction
Walter V-Drive
15" x 10" prop

Friends tell me this sounds rather large for an A4. I have a two blade feathering prop either Martec or Autostream 500 series that upon sea trial (high RPM little speed, feels like it is cavitating) and upon visual inspection while hauled appeared to have not enough pitch. I am not sure of the size or current pitch of the feathering unit. During the haul the prop was cleaned/scraped and mechanically seemed to be functioning. Before having it serviced I was trying to figure out what the pitch should be set to. I may just put on a fixed prop if I cannot get the featuring one to work.

-- Ken

[Kurt]

Nice boat! I have a 1976 C&C 33 MKI with an original Atomic 4. I can't offer you much prop advice, but I do know that the guy I bought my boat from 1.5 years ago said there was a folding prop on the boat when he bought it. He said the performance was so lousy that he decided to put the original fixed 2 blade prop back on the boat. It works fine and provides plenty of thrust in forward and reverse. My only complaint is that motoring into 15+ knot winds with some decent swell, I can only get about 4 knots. In decent conditions, I can get 5.5+ knots. I've been thinking about a three blade prop for when I go cruising, but haven't decided on it yet. I don't really know if a three blade prop would give me much more speed in bad conditions with a 10,000 pound boat.

[kwalters]

Kurt,
I checked the design specs again and I was off by an inch. 16x10x1 RH 2 blade was original equipment. If the original one was on the boat I would put it on and be done with it. Can you tell me what your RPMs look like at the speeds you mentioned? Thanks.
Ken

[Kurt]

My rpm at those speeds is 1800-1900 rpm. I rarely cruise over 1900 rpm.

[msauntry]

Kurt,
I've got the three blade Indigo on my Alberg 35 which is about 13,000 lbs boat (direct drive A4). It pushes me at 6.2 max speed, with easy cruising around 5.2-5.4 knot range. This is on a 24 foot waterline! I would endorse this as a great cruising prop for whenever you decide to go that route.
Its very well matched to the engine.

[scottneely]

indigo 3 blade prop

I've been thinking about getting one of these props for my irwin 28. does this prop really repel growth and barnacles?

Scott

[msauntry]

That is a risk you'll have to take for yourself. First year, I put mine on unpainted but with a zinc since I don't have a galvanic isolator (which it requires if you go zinc-less). Barnacles did grow. This year I tried the Petit Zinc spray paint and it stayed pretty clean for most of the season. I recently scraped about 8 small barnacles off it, mostly by the hub.