Reply
 
Thread Tools Search this Thread Display Modes
 
Old 09-06-2020, 04:16 PM   #1
Senior Member
 
Pmcsurf1's Avatar
 
City: St Augustine
Vessel Name: Agape
Vessel Model: Mainship 400 Trawler
Join Date: Feb 2020
Posts: 216
Fuel to injectors vs fuel to return

Isn't it true that more fuel returns to the tank than get sent trough the engine? Isn't also true that your fuel filter or filters are basically scrubbing fuel all the time?
My question. What percent of fuel gets burned vs returned?
__________________
Advertisement

Pmcsurf1 is offline   Reply With Quote
Old 09-06-2020, 04:23 PM   #2
Guru
 
Woodland Hills's Avatar
 
City: Jacksonville
Vessel Name: Alzero
Vessel Model: Hatteras 63' CPMY
Join Date: Apr 2017
Posts: 1,721
What make and model engine do you have? More information is needed to give an accurate answer.
__________________

Woodland Hills is offline   Reply With Quote
Old 09-06-2020, 10:50 PM   #3
Senior Member
 
City: San Diego, CA
Vessel Name: Freedom
Vessel Model: Hatteras 48 LRC
Join Date: Jan 2019
Posts: 222
Yes it is true but as mentioned varies based on engine. Detroit diesels return a lot, ford Lehmans 120 maybe .25 gals/hour.
READY is offline   Reply With Quote
Old 09-06-2020, 10:58 PM   #4
Guru
 
rgano's Avatar
 
City: Southport, FL near Panama City
Vessel Name: FROLIC
Vessel Model: Mainship 30 Pilot II since 2015. GB-42 1986-2015. Former Unlimited Tonnage Master
Join Date: Oct 2007
Posts: 3,314
I would assume that Mainship has one or two Yanmars. My single Yanmar 315 HP is likely a bit smaller that the single six they use in some MS trawlers but larger a with probably a wholly different injector pump. However, for what it is worth, I equipped my boat with a Floscan which can tell me how many gallons per hour go into the engine and how many are returned. Up at fast cruise, I see 21 GPH going in and about 11 GPH being returned. The reason there is so much return is because the fuel is also used to cool part of the engine. If you have a return fuel cooler, located in the seawater cooling hose just after the seawater cooling pump, you probably have more fuel being returned than being used by the engine.
__________________
Rich Gano
FROLIC (2005 MainShip 30 Pilot II)
Panama City area
rgano is offline   Reply With Quote
Old 09-08-2020, 09:32 AM   #5
Guru
 
Join Date: Oct 2007
Posts: 1,122
And that is why you must ensure the fuel out tank is also the fuel return tank under normal circumstances. Otherwise you risk a fuel overfill / spill.
Chrisjs is offline   Reply With Quote
Old 09-09-2020, 07:46 PM   #6
Senior Member
 
Pmcsurf1's Avatar
 
City: St Augustine
Vessel Name: Agape
Vessel Model: Mainship 400 Trawler
Join Date: Feb 2020
Posts: 216
Quote:
Originally Posted by Woodland Hills View Post
What make and model engine do you have? More information is needed to give an accurate answer.
MS 400 single Yanmar 6lya stp 370 HP. Didn't know different engines returned varied that much.
Pmcsurf1 is offline   Reply With Quote
Old 09-09-2020, 07:48 PM   #7
Senior Member
 
Pmcsurf1's Avatar
 
City: St Augustine
Vessel Name: Agape
Vessel Model: Mainship 400 Trawler
Join Date: Feb 2020
Posts: 216
Quote:
Originally Posted by READY View Post
Yes it is true but as mentioned varies based on engine. Detroit diesels return a lot, ford Lehmans 120 maybe .25 gals/hour.
Curious what is a lot. 50%?
Pmcsurf1 is offline   Reply With Quote
Old 09-09-2020, 09:49 PM   #8
Guru
 
LarryM's Avatar
 
City: League City, TX
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 1,010
Quote:
Originally Posted by Pmcsurf1 View Post
Curious what is a lot. 50%?
In my case, Cummins 6BTA5.9-M 370 (each engine)

Fuel Consumption @ Rated Speed - 20 gal/hr
Approx Fuel Flow to Pump - 73 gal/hr
Approx Fuel Flow Return to Tank - 53 gal/hr

These engines return 73.6% of the fuel to the tank at WOT.
__________________
Larry
M/V Pelago
LarryM is offline   Reply With Quote
Old 09-09-2020, 10:06 PM   #9
Guru
 
oscar's Avatar
 
City: Bethlehem, PA
Vessel Name: Lady Kay V
Vessel Model: 1978 Hatteras 53MY
Join Date: Oct 2015
Posts: 1,105
My 8V71 Detroits return 40GPH. It's called "built in polishing". Due to the different injection system.
__________________
https://ladykay.blog/
oscar is offline   Reply With Quote
Old 09-10-2020, 12:46 AM   #10
TF Site Team
 
Comodave's Avatar
 
City: Au Gres, MI
Vessel Name: Never Say Never
Vessel Model: President 41 DC
Join Date: Jul 2015
Posts: 11,840
Yes, it does vary greatly depending on the engine. My Lehmans return very little but the Detroits in a previous boat returned more than they burned.
__________________
Boat Nut:
If you are one there is no explanation necessary.
If you arent one, there is no explanation possible.
Comodave is offline   Reply With Quote
Old 09-10-2020, 07:47 AM   #11
Guru
 
Woodland Hills's Avatar
 
City: Jacksonville
Vessel Name: Alzero
Vessel Model: Hatteras 63' CPMY
Join Date: Apr 2017
Posts: 1,721
My 12/71’s return so much hot fuel that the cabin sole over the tanks gets warm. This is great in the fall, but not so good in summer.
Woodland Hills is offline   Reply With Quote
Old 09-10-2020, 09:59 AM   #12
Guru
 
OldDan1943's Avatar
 
City: Aventura FL
Vessel Name: Kinja
Vessel Model: American Tug 34 #116
Join Date: Oct 2017
Posts: 7,621
Cummins QSB 5.9 engine

What percentage of fuel is returned to the tank.
__________________
The meek will inherit the earth but, the brave will inherit the seas.
OldDan1943 is offline   Reply With Quote
Old 09-10-2020, 10:17 AM   #13
Guru
 
LarryM's Avatar
 
City: League City, TX
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 1,010
Quote:
Originally Posted by OldDan1943 View Post
Cummins QSB 5.9 engine

What percentage of fuel is returned to the tank.
OldDan, There are quite a few QSB 5.9 models. Seaboard Marine lists the Cummins Marine Diesel Performance Curves for most of their marine diesels. You can find your specific numbers there.
__________________
Larry
M/V Pelago
LarryM is offline   Reply With Quote
Old 09-10-2020, 10:44 AM   #14
Guru
 
City: gulf coast
Join Date: Jun 2014
Posts: 3,441
Yes it is built in polishing especially if you run on low tank levels. then the fuel in cycled faster than if tank is full
bayview is offline   Reply With Quote
Old 09-10-2020, 12:37 PM   #15
Guru
 
OldDan1943's Avatar
 
City: Aventura FL
Vessel Name: Kinja
Vessel Model: American Tug 34 #116
Join Date: Oct 2017
Posts: 7,621
Quote:
Originally Posted by LarryM View Post
OldDan, There are quite a few QSB 5.9 models. Seaboard Marine lists the Cummins Marine Diesel Performance Curves for most of their marine diesels. You can find your specific numbers there.
Yes, it talks about consumption but does not indicate the % returned to the tank.
__________________
The meek will inherit the earth but, the brave will inherit the seas.
OldDan1943 is offline   Reply With Quote
Old 09-10-2020, 12:39 PM   #16
Guru
 
City: Rochester, NY
Vessel Name: Hour Glass
Vessel Model: Chris Craft Catalina 381
Join Date: Aug 2019
Posts: 3,527
The detailed specs on the second page of those performance charts show total fuel pumped, return to tank at WOT and burn at WOT. Looks like the few QSB 5.9 models I looked at all pull 50 gph from the tank at rated RPM, so return flow is less on the higher power models (as they burn more at full power).
rslifkin is offline   Reply With Quote
Old 09-10-2020, 01:40 PM   #17
Guru
 
OldDan1943's Avatar
 
City: Aventura FL
Vessel Name: Kinja
Vessel Model: American Tug 34 #116
Join Date: Oct 2017
Posts: 7,621
Quote:
Originally Posted by LarryM View Post
OldDan, There are quite a few QSB 5.9 models. Seaboard Marine lists the Cummins Marine Diesel Performance Curves for most of their marine diesels. You can find your specific numbers there.
Hmmm something does not add up. This must be without a load.


Avg. Fuel Consumption - ISO 8178 E3 Standard Test Cycle: l/hr [gal/hr] 49.7
Fuel Consumption at Rated Speed: l/hr [gal/hr] 76.2
Approximate Fuel Flow to Pump: l/hr [gal/hr] 189.3 Maximum Allowable Fuel Supply to Pump Temperature: C [F] 60.0
Approximate Fuel Flow Return to Tank: l/hr [gal/hr] 113.0 Approximate Fuel Return to Tank Temperature .................................................. ....................C [F] 65.6 Maximum Heat Rejection to Drain Fuel .................................................. ........................kW [Btu/min] 1.5 Fuel Transfer Pump Pressure Range............................................. .....................................kPa [psi] 76 Fuel Pressure - Pump Out/Rail ...Mechanical Gauge .................................................. ..................kPa [psi] N.A.
[13.1] [20.1] [50.0] [140] [29.9] [150] [84] [11]
[20885]
N.A. = Not Available
__________________
The meek will inherit the earth but, the brave will inherit the seas.
OldDan1943 is offline   Reply With Quote
Old 09-10-2020, 02:46 PM   #18
Guru
 
LarryM's Avatar
 
City: League City, TX
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 1,010
Quote:
Originally Posted by OldDan1943 View Post
Hmmm something does not add up. This must be without a load.


Avg. Fuel Consumption - ISO 8178 E3 Standard Test Cycle: l/hr [gal/hr] 49.7
Fuel Consumption at Rated Speed: l/hr [gal/hr] 76.2
Approximate Fuel Flow to Pump: l/hr [gal/hr] 189.3 Maximum Allowable Fuel Supply to Pump Temperature: C [F] 60.0
Approximate Fuel Flow Return to Tank: l/hr [gal/hr] 113.0 Approximate Fuel Return to Tank Temperature .................................................. ....................C [F] 65.6 Maximum Heat Rejection to Drain Fuel .................................................. ........................kW [Btu/min] 1.5 Fuel Transfer Pump Pressure Range............................................. .....................................kPa [psi] 76 Fuel Pressure - Pump Out/Rail ...Mechanical Gauge .................................................. ..................kPa [psi] N.A.
[13.1] [20.1] [50.0] [140] [29.9] [150] [84] [11]
[20885]
N.A. = Not Available
OldDan,

Your numbers above are l/hour not [gal/hour].

At Rated Speed or Full Power WOT 50 gal/hr is being supplied by the Lift Pump to the Injection Pump which is using 20.1 gal/hr to fuel the engine and is returning 29.9 to the tank. In this case ~60% (29.9/50.0=0.598) of the fuel supplied is being returned. That looks in line to me for a QSB5.9-380 HO.

Am I missing something?
__________________
Larry
M/V Pelago
LarryM is offline   Reply With Quote
Old 09-10-2020, 03:36 PM   #19
Guru
 
OldDan1943's Avatar
 
City: Aventura FL
Vessel Name: Kinja
Vessel Model: American Tug 34 #116
Join Date: Oct 2017
Posts: 7,621
Quote:
Originally Posted by LarryM View Post
OldDan,

Your numbers above are l/hour not [gal/hour].

At Rated Speed or Full Power WOT 50 gal/hr is being supplied by the Lift Pump to the Injection Pump which is using 20.1 gal/hr to fuel the engine and is returning 29.9 to the tank. In this case ~60% (29.9/50.0=0.598) of the fuel supplied is being returned. That looks in line to me for a QSB5.9-380 HO.

Am I missing something?
I knew it was L/hr. For some reason, when I copied it, the gah were cropped.

That "return to tank" percentage is a variable depending upon the RPM of the engine?
__________________
The meek will inherit the earth but, the brave will inherit the seas.
OldDan1943 is offline   Reply With Quote
Old 09-10-2020, 03:47 PM   #20
Guru
 
LarryM's Avatar
 
City: League City, TX
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 1,010
Quote:
Originally Posted by OldDan1943 View Post
and that is a variable depending upon the RPM of the engine?
In the case of a mechanical lift pump yes, but regardless of RPM, it will pump more than is being used to fuel the engine. Those specs and pump curve may actually be included in the factory service manual if you happen to have one.
__________________

__________________
Larry
M/V Pelago
LarryM is offline   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 04:50 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×