Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-28-2023, 06:20 PM   #1
Guru
 
motion30's Avatar
 
Join Date: Jan 2010
Posts: 1,166
Fuel economy

Just thinking. (I know often dangerous) has anybody pulled one propeller and just ran on one motor and what were the effects of fuel economy?
motion30 is offline   Reply With Quote
Old 05-28-2023, 06:30 PM   #2
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 20,262
Quote:
Originally Posted by motion30 View Post
Just thinking. (I know often dangerous) has anybody pulled one propeller and just ran on one motor and what were the effects of fuel economy?
PassageMaker Magazine had a story where a guy did that on a transit from Hawaii to the west coast. Donít remember what the details were but you might be able to find it online somewhere. I believe it was maybe a GB 42.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you arenít one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 05-28-2023, 06:48 PM   #3
Guru
 
motion30's Avatar
 
Join Date: Jan 2010
Posts: 1,166
I have been unable to find that article if anyone has a link I would greatly appreciate it
motion30 is offline   Reply With Quote
Old 05-28-2023, 07:05 PM   #4
Senior Member
 
RedRascal's Avatar
 
City: Bellevue
Vessel Name: Rascal
Vessel Model: Homemade
Join Date: Dec 2019
Posts: 302
I've heard of a couple with a Bayliner 38 that I believe pulled a prop to get more range for making longer jumps in the Caribbean. The 38 was what they had and running 1 engine gave them the range to get where they wanted to go. Maybe one of the guys from the Bayliner forum will have more details. It was a great tale of making what you have work.
RedRascal is offline   Reply With Quote
Old 05-28-2023, 07:05 PM   #5
Guru
 
Pete Meisinger's Avatar
 
City: Oconto, WI
Vessel Name: Best Alternative
Vessel Model: 36 Albin Aft Cabin
Join Date: Oct 2012
Posts: 3,059
I think it would make little or no difference.

pete
Pete Meisinger is offline   Reply With Quote
Old 05-28-2023, 07:07 PM   #6
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in the Great Lakes
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 12,457
Quote:
Originally Posted by motion30 View Post
Just thinking. (I know often dangerous) has anybody pulled one propeller and just ran on one motor and what were the effects of fuel economy?
While I think it would improve your economy slightly, typically most twin engine boats have smaller rudders. Before I tried that, I would try maneuvering and docking with one engine to see how that worked out.

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 05-28-2023, 07:23 PM   #7
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 20,262
The guy that did the Hawaii trip stopped midway and put the prop on the other engine and pulled the original propÖ
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you arenít one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 05-28-2023, 07:42 PM   #8
Guru
 
City: Rochester, NY
Vessel Name: Hour Glass
Vessel Model: Chris Craft 381 Catalina
Join Date: Aug 2019
Posts: 7,009
Unless the rudder drag penalty is severe, running on one with the other prop removed should save a little fuel on most boats. Chances are, it won't be enough to justify the reduced maneuverability and loss of redundancy. Plus, depending on how the boat is propped and its top speed, you might be significantly speed restricted to avoid overloading the running engine.
rslifkin is offline   Reply With Quote
Old 05-28-2023, 07:59 PM   #9
Moderator Emeritus
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Black Dog
Vessel Model: Formula 41PC
Join Date: Jul 2015
Posts: 20,262
Quote:
Originally Posted by motion30 View Post
I have been unable to find that article if anyone has a link I would greatly appreciate it
I donít have any of the old PMMs anymore and the new ones arenít that worthwhile IMO.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you arenít one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 05-28-2023, 08:01 PM   #10
Guru
 
tiltrider1's Avatar
 
City: Seattle
Vessel Name: AZZURRA
Vessel Model: Ocean Alexander 54
Join Date: Aug 2017
Posts: 4,011
The Hawaii transit guy did it so that he could run the engine more loaded. He could have made it running both engines but the engines would have been just above idle and not making the appropriate heat.

One gallon of diesel makes about 20HP for one hour in most diesel engines. It takes a fixed amount of HP to move a boat through the water. Doesn’t mater if you get all the HP out of one engine or Half out of two.

Now some HP does get absorbed by the internals of the engine. By using only one engine you will gain some marginal economy, you unfortunately will give this back with rudder drag when you compensate for a crabbing boat. In almost all twin engine boats there is no economy gain by running just one engine, prop or no prop.

Now some one is going to pipe up about how they shut one engine down and got 15% inprovment in fuel economy. What they will fail to mention is that they slowed down on one engine. The act of slowing down is what gave them the economy. It goes something like this. “I normaly cruise at 1500 RPMs. I found when I ran just one engine at 1500 RPMs I saved a bunch of fuel.” This is true but what else is true is that they traveled at 7.5 knots on two engines and 5.9 knots on one engine. Had they throttled both engines down to 5.9 knots they would have saved the same amount of fuel.
tiltrider1 is online now   Reply With Quote
Old 05-28-2023, 08:30 PM   #11
Guru
 
Delta Riverat's Avatar
 
City: Stockton
Vessel Name: Dream Catcher
Vessel Model: 1979 Island Gypsy 44 Flush Aft Deck
Join Date: Feb 2022
Posts: 630
If I was worried about saving 5% on fuel cost I wouldn't have bought a boat.

Prop on, prop off. Rinse and repeat. What's that worth in time and effort?

Hire a diver? Haul and remove? Put it back on?

Be my guest, I'm not doing it.
Delta Riverat is offline   Reply With Quote
Old 05-29-2023, 12:37 AM   #12
Senior Member
 
RedRascal's Avatar
 
City: Bellevue
Vessel Name: Rascal
Vessel Model: Homemade
Join Date: Dec 2019
Posts: 302
I think I found the couple that tried using just 1 prop on their Bayliner 38. They wrote a few books about their travels which are on Amazon. They must have worked something out because I think a 38 has about a 300 mile range and it's ways to Honduras and Guatemala.

https://www.amazon.com/Diamond-Lil-D...=UTF8&qid=&sr=

Blog here but I didn't surface anything quickly that spoke about the range of their boat. Diamond Lil's Adventures Maybe someone that is better at search can get the story if running one prop gave them materially better range.
RedRascal is offline   Reply With Quote
Old 05-29-2023, 12:46 AM   #13
Guru
 
North Baltic sea's Avatar
 
Vessel Model: Nordic Tug 37
Join Date: Sep 2015
Posts: 1,104
Hi,

Litle bit this topic "articel."

https://www.passagemaker.com/lifestyle/strategies-for-long-range-cruising-with-twin-engines-2

I think best way saveing consuptions is low cruising speed 2-3 knots under you hull speed.

NBs
North Baltic sea is offline   Reply With Quote
Old 05-29-2023, 01:37 AM   #14
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Vessel Name: Carquinez Coot
Vessel Model: penultimate Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 12,549
Run the boat like it was designed.

Lots of previous posts.

Reduce speed to increase efficiency, At six knots, my boat's fuel consumption is half that at seven knots.
__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 05-29-2023, 04:54 AM   #15
Guru
 
mvweebles's Avatar
 
City: Saint Petersburg
Vessel Name: Weebles
Vessel Model: 1970 Willard 36 Trawler
Join Date: Mar 2019
Posts: 6,488
Quote:
Originally Posted by Comodave View Post
PassageMaker Magazine had a story where a guy did that on a transit from Hawaii to the west coast. Donít remember what the details were but you might be able to find it online somewhere. I believe it was maybe a GB 42.
It was many years ago, but I remember that article. Was indeed a GB42. It seems unbelievable, but my memory is that he removed one prop and loosened the other. To balance engine hours, he dove on his boat and swapped props. I believe he was a single-hander.

The reduced drag of removing a fallow prop would be significant. Would definitely make enough of a difference on a trans-Pacific trip.

Even though I read the story with jaw on floor, I find my recounting above incredulous.

OP - why do you ask?

Peter
__________________
M/V Weebles
1970 Willard 36 Sedan Trawler
mvweebles is offline   Reply With Quote
Old 05-29-2023, 08:18 AM   #16
Guru
 
City: Rochester, NY
Vessel Name: Hour Glass
Vessel Model: Chris Craft 381 Catalina
Join Date: Aug 2019
Posts: 7,009
If you were planning to run like this regularly, folding or feathering props might be worthwhile. Much easier then removing a prop, plus it leaves the second engine able to be used if needed.
rslifkin is offline   Reply With Quote
Old 05-29-2023, 08:20 AM   #17
Guru
 
Portage_Bay's Avatar
 
City: Coupeville Wa.
Vessel Name: Pelorus
Vessel Model: Californian 42 LRC
Join Date: Oct 2015
Posts: 2,191
To find out if a given twin engine boat will burn less fuel by running on one you just have to try and see if it works. Some people claim it does. Tiltrider1 explains very clearly why it probably won't.

My very small data set of two boats says it's not worth the trouble. One had modern instrumentation that indicated % load and fuel consumption. The savings were not enough to matter and the % load on the running engine was far too high at anything more than minimum speed. The other boat is older with no such instrumentation but was clear within minutes the boat was all but unmanageable. Extreme rudder required to keep a good heading and crabbing through the water.

In both cases we did not pull the idle prop. It was a first effort to see if running on one was worth any theoretical fuel savings.

On the boater who swapped props mid transit to Hawaii. I recall reading the article and couldn't believe he did that. The risk / benefit calculation on that decision was in my opinion far out of balance. Apparently his goal was to run the single harder for proper engine loading at low speeds. I think there are better ways to address that concern. Either run on one engine to Hawaii and the other on another long passage or find a way to carry more fuel. It would not require a lot of extra fuel to run the boat at minimum speed and two or three times a day run her hard for 15 - 20 min.

Regarding economy. If one is looking to have a less expensive boat to run the fuel burn difference between twin and single is not a major savings. It's maintenance and repairs. For example I currently have twin CAT 3208s. It's time to replace the exhaust risers. I've got 4 to buy and install where a single inline 6 would have 1 riser.
__________________
Some things are worth doing simply because they are worth doing.
Portage_Bay is online now   Reply With Quote
Old 06-02-2023, 12:48 PM   #18
Guru
 
AlanT's Avatar
 
City: Gig Harbor, WA
Vessel Name: MoonShadow
Vessel Model: Wendon Skylounge 72'
Join Date: Oct 2012
Posts: 701
I recently had to run my boat on one engine for a day. One thing to bear in mind is that the offset rudder angle required to compensate for offset propulsion constantly changes with changes in engine speed and, I suppose, current. At low idle my small rudders were unable to compensate for offset and I was only able to turn in one direction and when trying to drive straight the boat would crab somewhat. With increased engine speed rudder has more bite and therefore less angle required and it was possible to turn in both directions.
~A
AlanT is offline   Reply With Quote
Old 06-02-2023, 01:06 PM   #19
Member
 
City: Savannah
Join Date: Dec 2018
Posts: 14
U S navy would routinely on long cruises.
wrm95 is offline   Reply With Quote
Old 06-02-2023, 01:08 PM   #20
Guru
 
tiltrider1's Avatar
 
City: Seattle
Vessel Name: AZZURRA
Vessel Model: Ocean Alexander 54
Join Date: Aug 2017
Posts: 4,011
Quote:
Originally Posted by wrm95 View Post
U S navy would routinely on long cruises.
Yes but why, I doubt it was for fuel consumption. More likely it was to do maintenance.
tiltrider1 is online now   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not 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 Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 11:41 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2023, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012