• Untitled Document

    Join us on March 29rd, 7pm EST

    for the CBEC Virtual Meeting

    All EYO members and followers are welcome to join the fun and get to know the guest speaker!

    See the link below for login credentials and join us!

    March Meeting Info

    (dismiss this notice by hitting 'X', upper right)

Prop size/style

Denise McDonald

Member II
Greetings, I’m new to the group... thanks for the add!
We currently have our boat out for bottom painting and shaft replacement. We happened to find an old prop in a cubby onboard (the previous owner had told us it was there) but when we held it up to the current prop, it was much bigger. I should also mention that both are two blade props. We are looking to get a new prop while it’s out of the water but are confused as to what to get. I’m thinking a 3 blade for sure but size? Our engine is a Volvo MB10A gas powered 15 hp with 2000 max rpm rating. Any suggestions or direction where I can research will be greatly appreciate.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
What size/model boat do you have?
Max size of a prop is limited by closeness to the hull when the blade passes by. I seem to recall that tip clearance should be something over one shaft diameter (so if a boat has a one inch shaft, that clearance should be about 1.5 inches; the idea is to minimize the high frequency of the little slugs of water that each blade throws against the hull on each pass.)

After using a two blade fixed, a two blade featherer, and nowadays a narrow-blade 3-blade fixed, the last one gives us the most push under power. We do lose over a half knot of speed under sail, tho.

Please put in you "signature" entry with boat model, engine, and sailing (geographic) area. This helps us help you.
Welcome to the group!
:egrin:
 

Denise McDonald

Member II
What size/model boat do you have?
Max size of a prop is limited by closeness to the hull when the blade passes by. I seem to recall that tip clearance should be something over one shaft diameter (so if a boat has a one inch shaft, that clearance should be about 1.5 inches; the idea is to minimize the high frequency of the little slugs of water that each blade throws against the hull on each pass.)

After using a two blade fixed, a two blade featherer, and nowadays a narrow-blade 3-blade fixed, the last one gives us the most push under power. We do lose over a half knot of speed under sail, tho.

Please put in you "signature" entry with boat model, engine, and sailing (geographic) area. This helps us help you.
Welcome to the group!
:egrin:
Thank you Loren! We have a 1975 Ericson 27
 

JPS27

Member III
After much tinkering and experimenting on props for my e27, I settled on a 3 blade fixed Michigan prop. For reasons Loren mentioned, the 3 blade fixed was the one for me. Power up, but more importantly stop the vessel on a dime coming into my slip. I worked with a professional prop shop in the area.
 

wynkoop

Member III
JPS27 how did you get a 2gm15 in your boat? I would think it would be a bit too long for the E-27 engine space.
 

Denise McDonald

Member II
After much tinkering and experimenting on props for my e27, I settled on a 3 blade fixed Michigan prop. For reasons Loren mentioned, the 3 blade fixed was the one for me. Power up, but more importantly stop the vessel on a dime coming into my slip. I worked with a professional prop shop in the area.
Thank you! I believe will definitely be going for a three blade prop. It’s just getting the right size that’s still a question
 

wynkoop

Member III
A local power boater who I spoke to via Ham Radio a couple of weeks ago said if one calls S & S propellers and can provide them with the current propeller information, your boat make/model, your engine make/model, and an rpm vs speed table they can tell you which of their props will give you the performance you seek.

I have not followed up on this because I have yet to do a solid set of sea trials on Silver Maiden since the engine swap. Once I do the sea trials if I am not happy I will probably call S & S. From what I understand they are located on Long Island.

What I remember about propellers from Naval Arch classes would not fill a thimble. It seems some things just drop off the stack.
 

Nick J

Sustaining Member
Moderator
Blogs Author
I just went down this path and settled on a Campbell Sailor 3 blade fixed prop from West by North. Their recommendations seem way off from what other prop shops quote, but their design is significantly different. After asking around here and getting great reviews, I trusted what Kelsey from West by North recommended. I don't have a lot to compare it to, but I couldn't be happier with what they provided. All of the vibration from the 2 blade is gone, I don't notice any significant increase in drag, and the cruising and Max rpm speeds quoted were spot on. It was only $50 more than most of the other quotes I got for Michigan Wheel props as well.

 
Top