Prop choice - SailNet Community
 
LinkBack Thread Tools
post #1 of Old 03-20-2012 Thread Starter
clueless
 
Join Date: Aug 2009
Location: Houston/Austin
Posts: 184
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 6
 
Prop choice

So i have a Cal 29 which the last owner repowerd with a Volvo 2002 Diesel.
I am sure it still has the 3 blade prop from the A-4. Being the a4 prop was designed for rpm not torque. What prop should i be using? Everyone i ask just scratches their head " or something else" and says... " No clue, then walks off..
Any suggestions?

The reason i ask is plain that the boat in heavy stuff just seems to loose ground while the engine never seems to load up. As if the engine wants a prop with a higher pitch.

Thanks in advance for your time.
dieselboy is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of Old 03-20-2012
Courtney the Dancer
 
jrd22's Avatar
 
Join Date: Nov 2000
Location: San Juan Islands., WA, USA
Posts: 3,883
Thanks: 4
Thanked 22 Times in 21 Posts
Rep Power: 15
 
Re: Prop choice

You'll have to figure out what prop you have on now, the diameter and pitch are usually stamped into the prop. A prop shop should be able to calculate which prop should work with your boat and engine.

John
SV Laurie Anne

1988 Brewer 40 Pilothouse

jrd22 is offline  
Quote Quick Reply Share with Facebook
post #3 of Old 03-20-2012 Thread Starter
clueless
 
Join Date: Aug 2009
Location: Houston/Austin
Posts: 184
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 6
 
Re: Prop choice

Quote:
Originally Posted by jrd22 View Post
You'll have to figure out what prop you have on now, the diameter and pitch are usually stamped into the prop. A prop shop should be able to calculate which prop should work with your boat and engine.
Actually i did. Clueless was what i got. While im sure they know how to sell a prop and to repair one. The repower prop selection left them in the dark.
But it was a good idea, maybe i just need a better prop shop. lol
dieselboy is offline  
Quote Quick Reply Share with Facebook
post #4 of Old 03-20-2012
Just another Moderator
 
Faster's Avatar
 
Join Date: Sep 2005
Location: New Westminster, BC
Posts: 16,337
Thanks: 101
Thanked 303 Times in 293 Posts
Rep Power: 10
     
Re: Prop choice

Quote:
Originally Posted by dieselboy View Post
...., maybe i just need a better prop shop. lol
I'd say so!

There are several on line prop vendors that will give you that data as long as you have your displacement numbers, boat type and engine/gear combo.

Here's one... input your numbers and you should get some idea.. I'd still check this with a sailboat prop outfit.

http://vicprop.com/displacement_size.php

Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)

Last edited by Faster; 03-20-2012 at 02:28 PM.
Faster is offline  
Quote Quick Reply Share with Facebook
post #5 of Old 03-20-2012
Tartan 27' owner
 
CalebD's Avatar
 
Join Date: Jan 2008
Location: NYC
Posts: 4,714
Thanks: 4
Thanked 105 Times in 97 Posts
Rep Power: 8
 
Dock
Re: Prop choice

So, Cal 28' weighs about 8000# (4 tons)
Volvo Penta 2002 is an 18HP diesel
Prop is probably an Indigo A4 optimized prop which is a 3 blade 10" x 7.4" pitch Boat Seem Underpowered?
Other factors to consider: your prop is not in an aperture and thus should get good bite out of the prop flukes.
If you feel under powered (what rpms do you run your engine at?) it is not so much the pitch (~7") as the diameter that I'd question as being inadequate.

I know that this is not entirely comparable but folks with an Atomic 4 in their Catalina 30's use a 2 blade 12"x6" (or 7") prop and report that it works fine.
I use a 13" x 8" on my 7200# boat with our A4 but our prop is in an aperture between the keel and rudder.
The wider diameter of the prop gives it much more surface area to push against the water. The pitch will always be in the 6" - 8" range most likely.
Try to find a used 12"x6" (or7") 2 blade prop and try it out.
If you want to stay with a 3 blade prop I'm not sure what dimensions would work best for you as I'm more familiar with 2 blade fixed props. You can have a good prop shop take your existing 3 blade 10" prop and they can add material to the flukes to make it 11" or 12". They can also modify the pitch if you want.
First you need to find a good prop shop though.

"The cure for anything is salt water~ sweat, tears, or the sea." ~Isak Denesen

Everybody has one:

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CalebD is online now  
Quote Quick Reply Share with Facebook
post #6 of Old 03-21-2012
Senior Member
 
JimsCAL's Avatar
 
Join Date: May 2007
Location: Glen Cove, NY
Posts: 2,680
Thanks: 2
Thanked 60 Times in 55 Posts
Rep Power: 9
 
Re: Prop choice

If its the prop from the A4, its almost certainly too small and with too fine a pitch. Most A4s are direct drive while most diesels have a 2:1 or higher gear ratio. That means the correct prop will be larger in diameter and with a higher pitch. You need to know the engine model number and reduction ratio to get a proper selection. Take the info to a local prop shop or go to one of the online propeller suppliers and they should have no trouble giving you a recommendation.
JimsCAL is offline  
Quote Quick Reply Share with Facebook
post #7 of Old 03-21-2012
Senior Member
 
jsaronson's Avatar
 
Join Date: Dec 2011
Posts: 965
Thanks: 5
Thanked 28 Times in 28 Posts
Rep Power: 4
 
Prop choice

You need to be sure a bigger prop will not be too close to the hull. On myP28 they put in a shaft that was 1 inch longer when it was repowered with a diesel to accommodate the bigger prop.

The Office
c&C 35/3
Annapolis
jsaronson is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
1 inch prop on 25mm prop shaft? lawsonmitchell Gear & Maintenance 12 07-12-2014 06:50 PM
Feathering Prop vs. Fixed Blade Prop Benevento Pacific Seacraft 70 02-11-2011 07:52 AM
New Prop & Shaft - install prop questions preservedkillick Gear & Maintenance 2 05-22-2010 08:46 AM
Prop/Prop-Shaft Key Size? Skipaway Gear & Maintenance 7 07-29-2008 09:04 PM
Zincs for Sail Prop feathering prop jrbarn Gear & Maintenance 4 09-20-2006 10:40 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome