Impeller size - SailNet Community
LinkBack Thread Tools
post #1 of 3 Old 02-24-2010 Thread Starter
Senior Member
Join Date: Oct 2009
Location: Pennsylvania
Posts: 706
Thanks: 11
Thanked 2 Times in 2 Posts
Rep Power: 8
Impeller size

I repowered last winter going from the original 1986 Westerbeke 46 (with a bad cylinder) to a new Westerbeke 55 in my Cape Dory MS 300. I'm kind of surprised that the impeller on the 55 is only a small fraction of the size of the impelller from the old 46, maybe only 20%-25%. The old impleller from the 46 is larger in both diameter and width.

Do the water pumps on more recent engines operate at higher RPM's than older models? Does that account for the reduction in size? I was thinking that a larger engine would need at least as much cooling as a smaller older model.
LinekinBayCD is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
post #2 of 3 Old 02-24-2010
Senior Member
Join Date: May 2006
Posts: 201
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
There are a number of factors involved, not just relating to the impeller size or pump volume. It also includes the heat exchanger and its efficiency....
r.furborough is offline  
Quote Quick Reply Share with Facebook
post #3 of 3 Old 02-24-2010
Senior Member
Join Date: Oct 2009
Location: Gloucester, MA
Posts: 586
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
As said above, there are several factors at play.

The first thing to look at is the amount of energy going into heating the block. Modern engines tend to do a better job of converting the engine in the fuel into useful work rather than heat in the block and exhaust.

What determines the amount of energy taken out by the cooling water is the temperature increase in the water and the flow rate. If you have a better heat exchanger, it will increase the temp more requires less flow. In addition, the design of the cooling system could be getting much more efficient flow requiring a smaller impeller.

There is also the possibility that the previous impeller was much larger than necessary. On engines with thermostats, you can run a very large cooling circuit which is bypassed by the thermostat most of the time.

As long as it isn't running hot, I wouldn't worry about it.
klem is offline  
Quote Quick Reply Share with Facebook

Quick Reply

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

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


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

Email Address:


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
Impeller replaced, but did I screw up? countrygent5201 Gear & Maintenance 17 02-24-2010 06:50 PM
Sea Water Pump Impeller nauticalrich Gear & Maintenance 3 03-19-2003 08:20 AM
winch size maestro Gear & Maintenance 6 12-19-2002 08:09 PM
Size Matters Don Casey Buying a Boat Articles 0 04-05-2002 07:00 PM

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