Cruising rpm's - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #1  
Old 10-26-2009
Gulfislander's Avatar
Member
 
Join Date: Aug 2006
Posts: 70
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 9
Gulfislander is on a distinguished road
Cruising rpm's

I have a 3 year old Yanmar 2GM20FC. I understand that the maximum rpm's are ~3500. How do you determine what is the best cruising rpm's.
Reply With Quote Quick reply to this message Share with Facebook
  #2  
Old 10-26-2009
celenoglu's Avatar
Senior Member
 
Join Date: Dec 2008
Posts: 580
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 7
celenoglu is on a distinguished road
The cruising RPM for your Yanmar is 2000 -2800. This depends mainly on your needs and the boat's hull speed. Normally it is best to attain speeds near to hull speed without too much load on the engine. My cruising rpm's are 2200 -2500 for my Yanmar which means 5,5 -6 knots.
Reply With Quote Quick reply to this message Share with Facebook
  #3  
Old 10-26-2009
Gulfislander's Avatar
Member
 
Join Date: Aug 2006
Posts: 70
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 9
Gulfislander is on a distinguished road
My boat is a Niagara 31. I'm not sure of the hull speed but I think it's approx 5.5 knots. She seems to motor along nicely at 2800 rpms at 5.5 knots. But a friend told me I should only be cruising at 2000 rpm's.
Reply With Quote Quick reply to this message Share with Facebook
  #4  
Old 10-26-2009
St Anna's Avatar
Senior Member
 
Join Date: Mar 2003
Location: Southern QLD, Bayside
Posts: 1,428
Thanks: 1
Thanked 1 Time in 1 Post
Rep Power: 12
St Anna is on a distinguished road
Look at the performance curves. One will be torque and RPM - Another will be Fuel consumption, although it may be in grams of diesel & you will have to convert it.

A max torque will end generating max HP to the Prop and you can see what is best cruising RPM for your yacht. Always will be a compromise. Revs or speed
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #5  
Old 10-26-2009
Senior Member
 
Join Date: Feb 2008
Location: N. VA
Posts: 656
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 7
dacap06 is on a distinguished road
Send a message via Yahoo to dacap06
around .75 * max RPM ...

Over the years sailing OPBs, most folks ended up cruising at around 75% of max RPM or whatever got them to hull speed, whichever was lower.

My 30' Islander Bahama goes about 6.5 knots at 2700 RPM, which is 75% of my 2GMF's 3600 max RPM. My hull speed is 6.64 knots, so that's about right.

Those who do not know their hull speed should check out this Sailcalc page. It shows you all kinds of interesting statistics about your brand, size, and model boat (assuming it is on the list). I have no idea how accurate it is overall, but it was pretty close when I spot-checked a couple of its statistics for my boat using the original formulae.

Tom
__________________
T. P. Donnelly
S/V Tranquility Base
1984 Islander 30 Bahama
Pasadena, MD
Reply With Quote Quick reply to this message Share with Facebook
  #6  
Old 10-26-2009
sailak's Avatar
Crealock 37
 
Join Date: Apr 2007
Location: Alaska
Posts: 492
Thanks: 13
Thanked 14 Times in 14 Posts
Rep Power: 8
sailak is on a distinguished road
Quote:
Originally Posted by celenoglu View Post
The cruising RPM for your Yanmar is 2000 -2800.
What is that RPM range based on?

Thanks
__________________
Dale

S/V Elnora
Pacific Seacraft "Crealock" 37 #312

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #7  
Old 10-26-2009
Banned
 
Join Date: Nov 2002
Location: New York
Posts: 5,823
Thanks: 0
Thanked 14 Times in 14 Posts
Rep Power: 0
bubb2 has a spectacular aura about bubb2 has a spectacular aura about bubb2 has a spectacular aura about
By Ear! The boat will tell you where she is the most "comfortable." I have the same engine in a Beneteau. 2100 rpm's gives me 5.4 knots and I burn 1/4 gallon a hour. 2800 rpm's I am moving along at 6.4 + knots, but I am burning 1/2 gallon a hour.

Depending on wind and waves she will settle in somewhere between those two, but you can "feel" where she (the boat) wants to be.
Reply With Quote Quick reply to this message Share with Facebook
  #8  
Old 10-26-2009
rikhall's Avatar
old guy :)
 
Join Date: Feb 2008
Location: Fredericton, NB, Canada
Posts: 1,037
Thanks: 12
Thanked 14 Times in 12 Posts
Rep Power: 7
rikhall will become famous soon enough
Quote:
Originally Posted by bubb2 View Post
By Ear! The boat will tell you where she is the most "comfortable."
Bubb2 is totally right! An old Yanmar rep from Down Under told me - "Run her where she sings to you"

Our old Tanzer 28 - 2GM20F - 2400 RPM
Our "new-to-us" Irwin Citation 34 - 2QM20H - 2500 RPM

And yes, she does sing when it is good - she "shakes, rattles and rolls" when it is not good.

Cheers

Rik
__________________
Irwin Citation 34
Mystery
Reply With Quote Quick reply to this message Share with Facebook
  #9  
Old 10-26-2009
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,285
Thanks: 0
Thanked 79 Times in 70 Posts
Rep Power: 8
mitiempo will become famous soon enough mitiempo will become famous soon enough
I agree you should run where it seems comfortable. If you are not sure of your hull speed here's the formula: 1.34 x square root of waterline length. Example: 25' waterline, square root is 5 (5x5=25). 5 x 1.34 = hull speed which is approxmately 6.7.
Brian
Reply With Quote Quick reply to this message Share with Facebook
  #10  
Old 10-26-2009
captbillc's Avatar
ancient mariner
 
Join Date: Jul 2008
Location: duluth ,minnesota
Posts: 430
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
captbillc is on a distinguished road
my nimble 30 express has a yanmar 2GM 20F . LWL 25.8 beam 9.4 displacement 6,500 . 15"X11" pitch - perfect pitch prop. i cruise at 2200 RPM & 5.5kn at 3600 rpm (top) 6.9 kn.
__________________
Liberals are people who care about others. Freethinkers are not constrained by the myths of religion.
Reply With Quote Quick reply to this message Share with Facebook
Reply

Quick Reply
Message:
Options

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:
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:

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

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Retirement Cruising Budgets Randy Harman Cruising Articles 0 05-12-2004 09:00 PM
Calculating the Cost of Cruising Paul & Sheryl Shard Cruising Articles 0 04-03-2003 08:00 PM
Calculating the Cost of Cruising Paul & Sheryl Shard Her Sailnet Articles 0 04-03-2003 08:00 PM


All times are GMT -4. The time now is 12:04 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.