Lehman 120 FloScan readings

[2bucks]

Here is a series of pictures from my 1980 Lehman 120. Your engine may burn the same of different amounts of fuel at these rpm.

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[2bucks]

A few more

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[Daddyo]

2bucks,

YOU ARE THE MAN!! I've got some of this stuff wrote down here and there but now it's always a click away!

THANKS!!


-- Edited by Daddyo on Saturday 27th of August 2011 06:49:34 PM

 

[Tony B]

This is great stuff and is exactly what I have been wanting since I am in the trawler buying mode.
One more question......do you have any speed data that could be turned into MPG or any out and out MPG figures at various RPM's?

Thanks in advance

Tony B

 

[motion30]

2bucks
great info have those readings been consistent for you At what rpm do you cruise at? THANKS

 

[Codger2]

2bucks:

That's about the best AD for FloScan that I've ever seen! I must admit, I like your gage much better than mine.


-- Edited by SeaHorse II on Sunday 28th of August 2011 10:12:45 AM

 

[2bucks]

Tony B wrote:
This is great stuff and is exactly what I have been wanting since I am in the trawler buying mode.
One more question......do you have any speed data that could be turned into MPG or any out and out MPG figures at various RPM's?

Thanks in advance

Tony B

*I toyed with taking shots of the speed to go with the gph, but with tides, boat length, clean or dirty bottom, prop size, etc.*it would be pretty difficult to get an exact match to anyone else's boat. For my 40 trawler 1750 rpm is about 7 knots, 1600 about 6.5 and 1500 about 6.1. I almost always travel with the tide, so my actual speed will be higher for each rpm range.

I've been out for almost 3 months right now and have been doing most cruising at 1500 - 1550 just because I'm in no hurry. If I'm facing a 40 mile trip that I'm going to make in one shot, then I'll kick it up to 1750.

 

[bobofthenorth]

Put em on a graph guys.* I won't bother posting the graph because its easy to DIY but its a really good curve, increasing consumption at higher RPM - exactly what you would expect.

 

[Codger2]

2bucks wrote:
*I toyed with taking shots of the speed to go with the gph, but with tides, boat length, clean or dirty bottom, prop size, etc.*it would be pretty difficult to get an exact match to anyone else's boat.

_______________________________________________________________

Not to mention nicked prop, partially fouled injector, fuel leak and other gremlins that affect your gph reading. Remember, A FloScan will tell you much more than just your fuel flow but having accurate fuel flow info is enough reason to have one.

*

 

[markpierce]

SeaHorse II wrote:
2bucks:

That's about the best AD for FloScan that I've ever seen! I must admit, I like your gage much better than mine.

*Walt, I have*a similar*gauge as you*but it doesn't read nearly as high as 32 MPG.* We just need to look at our separate*tachometers also.

*


-- Edited by markpierce on Sunday 28th of August 2011 09:01:37 PM

 

[2bucks]

Man, I wish mine read 32 MPG. Although I'll bet you meant 32 GPH.

Ken

 

[markpierce]

2bucks wrote:
Man, I wish mine read 32 MPG. Although I'll bet you meant 32 GPH.

Ken

*Doh!

* That's the second time in a week I've made a fool of myself.

 

[Darren]

Are these shots taken in gear while moving or at the dock in neutral?
Darren

 

[2bucks]

Darren wrote:
Are these shots taken in gear while moving or at the dock in neutral? Darren

*In gear, cruising down the water.

 

[r-rossow]

I have been considering Flo Scans, but as I have twins (engines that is)*sucking fuel from*a fuel manifold that serves*both mains + generator there seems to be no way I could calibrate them properly.

Any smart ideas guys?*

 

[FF]

After the supply manifold the sender for each engine is installed.

Before the return is joined to a common return the other sender is installed.

No problem, just paying for 2 systems.

I have long thought that some of the Bosch style injection systems , those that return almost nothing, could use a gas engine system.

Some injection returns basically just return internal leakage , the error would not be meaningful.

 

[2bucks]

Check out the FloScan web site for installations with twins. IIRC you have the choice of one guage with a switch to look at each engine seperately, or a guage with two readouts.

The sensors for flow need to be installed past where the supply line splits to go to each engine so you can monitor each engines performance seperately. Depending on your engine room, you might want mount the sensors and pulse dampners remotely and then replumb the supply line to the engine rather than trying to find real estate right at the engine.

Ken

 

[JohnP]

Very interesting, really impressed with fuel burn at lower RPMs.

Thanks Ken for posting these images.

JohnP

 

[motion30]

ok so I have been on the icw for a week now Fueled up today. dropping my RPM to 1600 from 18oo changed my gph from 2.3-2.5 to 1.75 thanks again

 

[Nomad Willy]

While you guys are roll'in around on the ground think'in how clever you are you should consider the fact that all your numbers are meaningless without knowing if Ken's boat has been propped properly. If he's overpropped even 100 rpm ...fuel burn at 1750 on your boat could be way different than his. Ken's numbers will only be valid if you're propped just about exactly the same as he is and have a boat very very similar in displacement and shape. On the bright side you can tell quite a bit about what happens to the burn rate if you increase or decrease say 100 or 200 rpm.

 

[FF]

A FloScan will tell you much more than just your fuel flow but having accurate fuel flow info is enough reason to have one

They work great as a fuel gauge too, if you know your tanks capacity.

 

[Andy G]

This question has been raised in other posts, but in relation to the flow scan figures posted here, how would you expect the consumption to differ if the boat was running twin FL120 insead of a single. I seem to remember that the consensus was with a twin set up, each engine would use approximatly 30% less fuel for the same RPM/MPG figures.

Is this a valid assumption?

 

[motion30]

nomadwilly wrote:
While you guys are roll'in around on the ground think'in how clever you are you should consider the fact that all your numbers are meaningless without knowing if Ken's boat has been propped properly. If he's overpropped even 100 rpm ...fuel burn at 1750 on your boat could be way different than his. Ken's numbers will only be valid if you're propped just about exactly the same as he is and have a boat very very similar in displacement and shape. On the bright side you can tell quite a bit about what happens to the burn rate if you increase or decrease say 100 or 200 rpm.

*all i can say* is it gave me the info to help me save a little fuel

 

[Andy G]

This post has got me doing the figures(estimates) on our IG 36.We only have sight lines, using some of the above figures and my own observations, plus some of Marin's observations from his GB 36, which is very similar in set up to our boat.

I am amazed that between 1500 & 2000 RPM we increase boat speed by 1.3 knots with a corresponding 98% increase in fuel consumption! Do any other twin Lehman owners find this plausable?

 

[Marin]

I find it plausible but we've never run any tests to determine fuel consumption increase between various rpm. A GB is no different than any other similar semi-planing boat--- you can run them faster than hull speed but the fuel penalty is significant.

This is somewhat apples and oranges, but in the GB 42 ads of the 1990s when they were still making the boat, peformance figures included in the ad called out an "economic" cruise speed of some nine knots with a fuel consumption of seven or eight gallons per hour (twin engine, 400-something hp Cats). However the boat could be cruised "comfortably" at some 14 or 15 knots with a fuel consumption of some 23-24 gallons per hour. So less than twice the speed at three times the fuel consumption.

 

[2bucks]

Andy, you are most likely exactly on the mark. I don't have my numbers with me now, but when I return in the spring (May 2012) I'll update this and give my speed numbers for each rpm range, which again, won't match anyone else, but will give an idea of fuel use/speed on my single. I cringe when someone posts that they usually run at "80% rpm" (2000 rpm or more) on a Lehman 120. You've got to be in a real hurry to want to burn that much fuel. And if you're in a hurry, you shouldn't be driving a trawler.