Mileage from an outboard - 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 04-02-2010
Junior Member
 
Join Date: May 2008
Location: Jacksonville, Florida
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
fredn56 is on a distinguished road
Mileage from an outboard

This may be a quirky question, leading to even quirkier answers, but here goes:

How many miles (or hours even) can you expect to travel on a river or Atlantic ICW given a 3000lb displacement fin keel sailboat under 8 hp 4 stroke Tohatsu outboard power only, not considering current?

Thinking about an extended trip this summer and wondering about gas tanks.

Thanks,

Fred Nelson
Reply With Quote Share with Facebook
  #2  
Old 04-02-2010
JimsCAL's Avatar
Senior Member
 
Join Date: May 2007
Location: Glen Cove, NY
Posts: 2,363
Thanks: 1
Thanked 31 Times in 30 Posts
Rep Power: 8
JimsCAL is on a distinguished road
Depends a lot on how hard you push the boat. Backing off even a little from the boat's hull speed will greatly reduce the fuel consumption. You don't give much info about the boat. If I had to guess, I would say about 1/2 a gallon per hour at around 5 knots, so figure a gallon every 10 miles.
Reply With Quote Share with Facebook
  #3  
Old 04-02-2010
zz4gta's Avatar
I don't discuss my member
 
Join Date: Aug 2007
Location: Chesapeake Bay
Posts: 2,421
Thanks: 0
Thanked 16 Times in 16 Posts
Rep Power: 7
zz4gta is on a distinguished road
I have a 3000 # boat but my outboard is only 3.5 hp w/ a 0.3 gal tank. I can get 25 minutes in a headwind (slowly), and dead calm I can motor for 45 minutes around 5 knots.
__________________
Merit 25 # 764 "Audrey"
Reply With Quote Share with Facebook
  #4  
Old 04-02-2010
tommays's Avatar
Senior Member
 
Join Date: Sep 2008
Posts: 4,228
Thanks: 1
Thanked 24 Times in 24 Posts
Rep Power: 6
tommays will become famous soon enough
Well

I would think you would move close to hull speed at 1/2+a bit throttle as my 4Hp dos that on the J24 with not much speed after 5 knots no matter what

When we use to take trips with the boat we allways had two 6 gallon tanks which will allow a full day of motoring under allmost any conditions
__________________
1970 Cal 29 Sea Fever

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

1981 J24 Tangent 2930
Tommays
Northport NY


If a dirty bottom slows you down what do you think it does to your boat
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #5  
Old 04-03-2010
TohatsuGuru's Avatar
Misanthrope
 
Join Date: Oct 2007
Location: Tampa
Posts: 115
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
TohatsuGuru is on a distinguished road
Too many varibables, but:

8 (4-str)
5,500 RPM
0.85 Gallons per hour
__________________
Elvin
Solution One Maritime
Reply With Quote Share with Facebook
  #6  
Old 04-03-2010
eMKay's Avatar
Senior Member
 
Join Date: Aug 2007
Location: Buffalo
Posts: 838
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
eMKay is on a distinguished road
Quote:
Originally Posted by TohatsuGuru View Post
Too many varibables, but:

8 (4-str)
5,500 RPM
0.85 Gallons per hour
That's full throttle though, which would be necessary to push my 7000lb boat, but not one weighing less than half that.

I would estimate 1/3 to 1/2 gallon per hour, 10-13mpg or so
__________________

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


Technician, RCR Yachts Buffalo.
Reply With Quote Share with Facebook
  #7  
Old 04-03-2010
tager's Avatar
Senior Member
 
Join Date: Nov 2008
Posts: 991
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 6
tager is on a distinguished road
I have a 5000 pound fin keeler, a Haida 26, with a Honda 8hp 4 stroke. It has a 21 foot waterline, and a calculated hull speed of around 6 knots. I normally keep the RPMS a little low, and go 4 knots, just starting to push a noticeable wake. This keeps me going at less than a gallon per hour.

I also motored this same boat with a Nissan 5hp 2 stroke at around 3 knots and less than half throttle, this didn't even put out a noticeable wake, and was painfully slow, but we used barely any gas at all, probably less than a half gallon per hour.

Wave making resistance - Wikipedia, the free encyclopedia

Your waterline length is going to be an important factor in determining how efficiently she will go through the water. A longer waterline means a higher hull speed.

Also, a high thrust prop will waste less gas than the stock prop.

I made the mistake of running my outboard at very low rpm for around 8 hours, and fouled the plugs, so keep that in mind, occasionally you should clear out the carbon by revving her up.
Reply With Quote Share with Facebook
  #8  
Old 04-03-2010
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 9 Times in 9 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
One thing no one has mentioned yet is the current. It depends on how well you time your passage to maximize the advantage of current... This can make a huge difference.

If your boat normally motors at 4.5 knots...and you're going against a 2 knot current, you're now doing only 2.5 knots, or 56% of your normally cruising speed... likewise, if you time it so that you're going with the current, you're now doing 6.5 knots or 144% of your normal cruising speed.
__________________
Sailingdog

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

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #9  
Old 04-05-2010
roline's Avatar
Cal 9.2 SilverSwan
 
Join Date: Jul 2000
Location: East Tennessee
Posts: 272
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 15
roline is on a distinguished road
Diesel has 16-18 hp per hr per gallon, and gas is 12 to 14 hp per hr per gallon.
I run a 2GM20 at 2800-2900 rpm at 40% prop slip for maximum efficiency.
Say 6 knots SOG at 78% of full power ( 80%) is the most efficient for diesels, I get over 15hrs cruising range at 6 knots= ~100 miles.


I did my calcs by using a gps and monitoring fuel usage. You would have to do the same with your setup be be sure of actual performance.
Attached Thumbnails
Mileage from an outboard-speed.jpg  
__________________
Cal 9.2 #19 SilverSwan
Reply With Quote Share with Facebook
  #10  
Old 04-05-2010
Member
 
Join Date: Feb 2003
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
JimB517 is on a distinguished road
Catalina 25

I have a Catalina 25, weighs about 6000 lbs cruise loaded. I have a Tohatsu 9.8 4 stroke. I usually motor sail at about 1/4 throttle, at 5 knots. I get 10 nautical miles per gallon. On a cruise I use a guesstimate of 15 nmpg because I try to sail as much as possible and during that time the motor is off (of course).

If I push the boat up to 6 knots the mpg goes WAY down.
Reply With Quote Share with Facebook
Reply


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
Outboard motor controls waltzingmatilda Gear & Maintenance 3 05-05-2010 09:08 AM
Inboard vs. Outboard greencaptn Boat Review and Purchase Forum 19 02-20-2007 08:05 AM
Outboard: Buying, Type & Fitting omega001 Gear & Maintenance 11 11-10-2006 10:09 AM
Caring for the Cruising Outboard Doreen Gounard Gear and Maintenance Articles 0 04-22-2003 08:00 PM
Outboard Motor Brackets Sue & Larry Gear and Maintenance Articles 0 09-04-2002 08:00 PM


All times are GMT -4. The time now is 02:28 AM.

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.