Overpropped; What to do? - Page 2 - SailNet Community
 7Likes
Reply
 
LinkBack Thread Tools
post #11 of 32 Old 01-25-2013 Thread Starter
Junior Member
 
Join Date: Jan 2013
Location: Luperon DR
Posts: 11
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Overpropped; What to do?

Ok. So, I ran out to Sombrero Key yesterday; the new prop has increased my RPM to a Max of 2950. It now seems to run pretty happy at 2200-2600 rpm. I'm reasonably happy with that, as the torque curve peaks and flattens around 2300... At least I'm in the power...

What's the consensus? You think that's still over-propped too much?

On another note, grant was telling me an inch of diameter roughly equates to an inch of pitch. So chucklesR, your 16/12- what rpm are you running with? (notwithstanding hull differences, you should be roughly the same RPMs??)
korn is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #12 of 32 Old 01-25-2013
Senior Member
 
chucklesR's Avatar
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,979
Thanks: 10
Thanked 31 Times in 31 Posts
Rep Power: 10
     
Re: Overpropped; What to do?

I can't answer that as I've just bought the boat and haven't checked.

Winter here, boat up for now. As a rule of thumb Grant is right.

Lessons learned are opportunities earned.
chucklesR is offline  
Quote Quick Reply Share with Facebook
post #13 of 32 Old 01-25-2013
Senior Member
 
Join Date: Feb 2010
Location: Narragansett Bay
Posts: 11,039
Thanks: 46
Thanked 224 Times in 209 Posts
Rep Power: 7
   
Re: Overpropped; What to do?

What did you determine was the max rated rpm of your motor? Full wide open throttle should settle within 100 rpm of that under load, given normal tachometer error. It is possible that your tach is way off though, so if you have the right prop and it is off by a ton, you should check that next.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Jeanneau 54DS

In the harsh marine environment, something is always in need of repair. Margaritas fix everything.
Minnewaska is offline  
Quote Quick Reply Share with Facebook
post #14 of 32 Old 04-14-2013
Member
 
Join Date: Feb 2013
Location: Mobile, AL
Posts: 34
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Overpropped; What to do?

Chuckles - wondering if you got your boat in water yet to see what RPM's turning. I have an Endeavour 38 I recently got with the yanmar 44hp 4JHE engine. Wondering if it has some fuel/injector issues.At the dock you can run it and get some white smoke that will clean out after running it a bit. Boat had sat up a year. Trying to drain as much fuel out as I can then probably drain the rest and see if that helps before new injectors. Cranks right up and runs smooth. Took it out yesterday and ran it awhile and when running the RPM's up to around 2900 on the tach it was rolling black smoke out the exhaust and smell unburned diesel. Has a 17x16 2 blade prop. Transmission is a Kanziki KBW20, 2.62:1 reduction. When you bring the RPM's down around 2000 to 2200 levels out fine and in flat water was doing around 6.5 to 6.8knots. Surveyor on sea trail thought it may be a little overpropped. Thinking if changing to use a 3 blade as like the extra bite when you need it. Not racing much anymore. Anyone have some thoughts
thanks
Last Mango
Endeavour 38
Mobile AL
last mango is offline  
Quote Quick Reply Share with Facebook
post #15 of 32 Old 04-15-2013
Senior Member
 
Join Date: Jan 2012
Location: British Columbia
Posts: 2,526
Thanks: 20
Thanked 39 Times in 37 Posts
Rep Power: 4
 
Re: Overpropped; What to do?

Give her full throttle, then back off slightly. If it slows down you are not overpropped., If you have to back the throttle off a long way before it begins to slow down, you are over propped.You can either cut it down or pitch it down. Ask what others are using on similar sized boats with similar sized engines and reductions.Pitch is not hard to calculate with a pocket calculator. Charts on diameter are available in books like Skenes Elements of Yacht Design.

Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"
Brent Swain is offline  
Quote Quick Reply Share with Facebook
post #16 of 32 Old 04-15-2013
Senior Member
 
chucklesR's Avatar
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,979
Thanks: 10
Thanked 31 Times in 31 Posts
Rep Power: 10
     
Re: Overpropped; What to do?

http://www.sailnet.com/forums/diesel...n-experts.html

Unfortunately I'm having other issues brought on by my own stupidity.

Lessons learned are opportunities earned.
chucklesR is offline  
Quote Quick Reply Share with Facebook
post #17 of 32 Old 04-15-2013
Member
 
Join Date: Feb 2013
Location: Mobile, AL
Posts: 34
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Overpropped; What to do?

Hey Chuckles
I'm there on a daily basis. If you learn by your mistakes I am a candidate for Mensa. Another few years and I'm equal with Einstein. Korn; I would have to go out again and write the RPM's and knots down, but seems like I can drop a good bit of RPM's and maintain the same speed or within 1/2 knot in flat water. Have to do some serious note taking.

Last Mango
Mobile AL
last mango is offline  
Quote Quick Reply Share with Facebook
post #18 of 32 Old 04-15-2013
Senior Member
 
Join Date: Jan 2013
Location: Montreal, QC, Canada
Posts: 338
Thanks: 0
Thanked 14 Times in 13 Posts
Rep Power: 3
 
Re: Overpropped; What to do?

Internal combustion engines are the most overall efficient at 75% of maximum RPM. The math is easy, 2700 rpm. It's a rule.
sony2000 is offline  
Quote Quick Reply Share with Facebook
post #19 of 32 Old 04-15-2013
Senior Member
 
chucklesR's Avatar
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,979
Thanks: 10
Thanked 31 Times in 31 Posts
Rep Power: 10
     
Re: Overpropped; What to do?

Quote:
Originally Posted by last mango View Post
Hey Chuckles
I'm there on a daily basis. If you learn by your mistakes I am a candidate for Mensa.
Last Mango
Mobile AL
I've been a member since I was 18. It don't mean nothing.

Lessons learned are opportunities earned.
chucklesR is offline  
Quote Quick Reply Share with Facebook
post #20 of 32 Old 04-16-2013
Senior Member
 
Join Date: Jan 2012
Location: British Columbia
Posts: 2,526
Thanks: 20
Thanked 39 Times in 37 Posts
Rep Power: 4
 
Re: Overpropped; What to do?

Quote:
Originally Posted by chucklesR View Post
I've been a member since I was 18. It don't mean nothing.
I hear there is a club for those on the other end of the spectrum. Its called "DENSA".
MedSailor and ottos like this.

Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"
Brent Swain 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
overpropped vs underpropped groundhog Gear & Maintenance 45 12-19-2012 10:20 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