Reply
 
Thread Tools Display Modes
 
Old 05-05-2011, 11:17 AM   #1
Newbie
 
Join Date: May 2011
Posts: 3
rpm and fuel consumption

New Trawler owner soon.** Curious about crusing rpm and fuel consumption on a Ford Lehman 120 HP, 2715E .* Engine has 5700 hrs.Looking at Trawler Forum and that doesnt seem over used.* Survey coming soon and it appears I should look for oil leaks and exhaust manifol discharge pipe ware. Any other ideas and help?
__________________
Advertisement

Plumber is offline   Reply With Quote
Old 05-05-2011, 02:57 PM   #2
Newbie
 
Join Date: May 2011
Posts: 3
RE: rpm and fuel consumption

36ft Universal, single, aft cabin
__________________

Plumber is offline   Reply With Quote
Old 05-05-2011, 03:34 PM   #3
Guru
 
JohnP's Avatar
 
City: Toms River
Country: USA
Vessel Name: D U E T T E
Vessel Model: 1996 36' Island Gypsy
Join Date: Dec 2009
Posts: 1,109
RE: rpm and fuel consumption

Plumber,* We run our 120 lehman between 1500 and 1800 rpm. Average about 2gph in the middle of that range.

Our boat is only 32ft and yours at 36ft should probably be a bit faster due to the longer waterline. We generally do only between 6.5 and 7.5 knots.

As you have stated the exhaust elbow should be looked at if it has more than 2000 hours.

Another thing to check is whether the raw water pump is the original design (Jabsco) or the much improved Johnson pump.

Once you know what you are looking for the Jabco is easy to spot because the four mounting bolts are located on a separate pump drive which is about four inches behind the front housing of the engine.. While the Johnson pump is connected directly to the front housing without any separate pump drive.

The pump drive is the problem, some of them break.* With 5700 hours this problem has probably been addressed.

The Lehman is very simple and reliable,* take* care of it and it should last and last.

Most of them are old already and just keep chugging along.

Good Luck. JohnP
JohnP is offline   Reply With Quote
Old 05-05-2011, 05:21 PM   #4
Guru
 
jleonard's Avatar
 
Join Date: Jun 2008
Posts: 2,740
RE: rpm and fuel consumption

I have a 40 Albin, single FL 120, run at 1700-1800, get about 6.5 to 7 knots, use less than 2 gph at that speed.

I did the Johnson upgrade when I bought the boat 4 seasons ago. Easy job.

Best of luck.
jleonard is offline   Reply With Quote
Old 05-05-2011, 08:15 PM   #5
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
RE: rpm and fuel consumption

Maybe you need a Flowscan or whatever to measure consumption (top-right gauge).
Attached Thumbnails
Click image for larger version

Name:	helmsman.jpg
Views:	390
Size:	178.6 KB
ID:	5907  
markpierce is offline   Reply With Quote
Old 05-05-2011, 08:44 PM   #6
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,724
RE: rpm and fuel consumption

Charles,

That depends a lot on the boat. For example my Willard would be running at less than 5.5 knots at that point. The Willard 40 makes 7 knots with almost half the power it takes to make that speed w a W30. At one time I thought hull speed was achieved when the bow started to rise but then discovered it happens considerably later (at a greater speed). You're right though Charles that that is a very economical speed to run.
Nomad Willy is offline   Reply With Quote
Old 05-06-2011, 12:40 AM   #7
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
RE: rpm and fuel consumption

It's hyperbolic.
markpierce is offline   Reply With Quote
Old 05-19-2011, 08:14 PM   #8
Guru
 
motion30's Avatar
 
Join Date: Jan 2010
Posts: 740
RE: rpm and fuel consumption

My 34' marine trader with a single 120 runs about 8mph at 1650 rpm and burns 2.4 gph
motion30 is offline   Reply With Quote
Old 05-19-2011, 08:15 PM   #9
Guru
 
motion30's Avatar
 
Join Date: Jan 2010
Posts: 740
RE: rpm and fuel consumption

one quick note I upgraded the oil filter hoses from the stock 5/16 hoes to 3/8'' hoses and picked up 10lbs of oil pressure
motion30 is offline   Reply With Quote
Old 05-19-2011, 11:17 PM   #10
Senior Member
 
Larry H's Avatar
 
City: Pacific Northwest
Country: USA
Vessel Name: Jacari Maru
Vessel Model: 2014 Ranger Tug R-27
Join Date: Nov 2010
Posts: 359
RE: rpm and fuel consumption

I have a 37 ft Puget Trawler (Taiwan built) with the FL 120. I run at 7 knots at 1600 rpm and get 2gph. When I got the boat I did the Johnson pump conversion, and changed the exhaust elbow. The exhaust elbow goes bad from the inside out. Oil leaks at the back of the engine may be from the fuel pump gasket. Change the oil and transmission coolers if they haven't been changed in the last 2 years. If you change the coolers, get the copper-nickel ones, a little more expensive, but a much longer life.
Larry H is offline   Reply With Quote
Old 05-20-2011, 05:55 AM   #11
Hospitality Officer
 
Andy G's Avatar
 
City: Pittwater
Country: Australia
Vessel Name: Sarawana
Vessel Model: IG 36 Quad Cabin
Join Date: Sep 2010
Posts: 1,557
RE: rpm and fuel consumption

I run twin FL120's in our IG 36'.

I am right in assuming that with both engines running, at say 1700rpm, they would use slightly less fuel each than say a single engine would powering a 36' would. if this is the case then what fuel consumption could I expect to get with this twin set up?
Andy G is offline   Reply With Quote
Old 05-20-2011, 07:54 AM   #12
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,724
RE: rpm and fuel consumption

Shrimp,

You should burn more fuel because of the much higher heat loss from two engines running. However I think you are implying that w 2 engines driving the boat at the same speed they would be doing less work each and burn less fuel. I'm sure that's true but the heat loss will prevent it from being a wash. I think Marin Faure runs his GB 36 w twin Lehmans at 3gph on each engine and I think he runs at 1800 rpm. Unless you're way up at the top end the less the load the less the efficiency. Keep in mind Shrimp that almost everybody calculates their fuel burn from engine hours (from the hour meter) and how many gallons it takes to fill up the tanks. All the idling and slow running gets mixed up in the numbers and now that fuel cost is high most do shorter trips and the less than cruise throttle engine time is a higher percentage of the total so most skippers burn considerably more than they claim. The difference could be as high as 25%. Those skippers that do very long trips like Larry H should have more accurate numbers. In answer to your question I'd say 4.5 to 5.5 gph. That may be at about 8 knots so slowing down to 7 should save at least 1.5 gph.
Nomad Willy is offline   Reply With Quote
Old 05-20-2011, 08:38 AM   #13
Guru
 
2bucks's Avatar
 
Join Date: Oct 2007
Posts: 698
RE: rpm and fuel consumption

I think your looking for actual experience so you will have a benchmark to start with on the new boat. I run a 1980 Lehman 120 in my 40' Puget Trawler. @1750 rpm I burn 2.0 GPH at 1850 I burn 3.1 GPH. These are from the FlowScan unit which has been calibrated with a couple thousand gallons of diesel thru it. At wide open throttle I can get almost 8 GPH to flow thru. At 1500 it drops to 1.3. Depending on your cruising style and how fast you want to get somewhere, you can run your engine as you see fit.

Oil coolers, the cupro/nickel variety should be considered suspect after a certain amount of time. In my cruising waters I look, scrape, and decide after about 5 years of use. I've not had a problem with that schedule in 32 years now. The coolers are available from American Diesel for $120 each plus shipping.

Exhaust elbows can be looked at annually. Dig around with some sharp pointy object with the intent to dislodge any carbon or to drive it thru the side of the elbow. You can also tap on the outside of the elbow with a hammer like object and sometimes hear the difference in the strength of the metal. I know thats a subjective test, but if you tap lightly on the outside and the hammer crackes the metal, you have serious deterioration inside. You can buy gaskets for the elbow at AD also for I think right around $3. An elbow is about $140.

Your raw water pump may or may not have been changed. The "Johnson" pump replacement is about $400 at AD. A careful examination can be made periodically, or you can do what I did and just make the change, keeping the old as a good spare if needed.

Good luck with your new purchase,

Ken
2bucks is offline   Reply With Quote
Old 05-20-2011, 09:01 AM   #14
Guru
 
jleonard's Avatar
 
Join Date: Jun 2008
Posts: 2,740
RE: rpm and fuel consumption

"you can do what I did and just make the change, keeping the old as a good spare if needed."

I recall plugging up an oil hole (with a supplied tapered pin) to the drive gear as part of the new pump installation. That would make the old water pump not usable as it requires oil. No?

*
jleonard is offline   Reply With Quote
Old 05-20-2011, 03:03 PM   #15
Rob
Veteran Member
 
Rob's Avatar
 
Join Date: Oct 2010
Posts: 74
RE: rpm and fuel consumption

On a FL 120 with that number of hours it would be nice if you had a decent history of oil analysis. You might be able to see wear patterns,water in the oil and what not. As far as the number of hours on the engine I personally would say that 5000 hours would probable be considered half life. The Lehman is a pretty basic and not real high end engine. Just My opinion! I have a FL 120 in my Willard 40 and burn 1.6 gal per hour @ 1550, I simply don't see that much advantage running the engine*much faster on our full displacement boat. One thing that you should look at might be the injection pump, I have seen several of these that have had there lube oil contaminated with fuel. Just look for very thin oil. This pump should have the lube oil changed every 50 hours, so if it has recently been changed you won't see any problem.

Rob Hays

Lady Anne, Willard 40 PH
Rob is offline   Reply With Quote
Old 05-20-2011, 04:43 PM   #16
Guru
 
2bucks's Avatar
 
Join Date: Oct 2007
Posts: 698
RE: rpm and fuel consumption

Quote:
jleonard wrote:
"you can do what I did and just make the change, keeping the old as a good spare if needed."

I recall plugging up an oil hole (with a supplied tapered pin) to the drive gear as part of the new pump installation. That would make the old water pump not usable as it requires oil. No?

*


*I suppose for those who did plug the hole it may be a problem long term. I understand many didn't plug the hole. (mine is plugged)*Since I plan to use mine as a spare because of some problem that a new spare impeller won't fix, I'm thinking that reduced oiling is probably a minor issue. If one were to use it as a spare (with the excess oil hole plugged)*for a long period of time, then you'll probably see some excess wear on the gears.

I'm optimistic that even a 24 hour run back to civilization would be possible.

Ken

*

*
__________________

2bucks is offline   Reply With Quote
Reply

Thread Tools
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
LRC 34/3208 fuel consumption Fighterpilot Californian 4 04-21-2011 06:07 PM
Fuel Consumption..3406 Cat floorme1 Power Systems 6 03-31-2011 04:56 AM
Fuel Consumption with a 40' CHB kimbo Taiwanese Makes 30 01-05-2011 09:29 PM
Fuel consumption floorme1 General Discussion 4 09-12-2010 09:56 PM




All times are GMT -5. The time now is 04:10 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012