T&T: Fuel flow meter

[Milt Baker]

With a Lehman 120, you don't need a fuel flow meter!  What you need is a fuel consumption chart.

Just MEASURE your fuel consumption at various RPMs and then make up a table which shows fuel consumption.  Without naming brand names, in my experience fuel flow meters are temperamental creatures that are wrong more often as they're right, and an accurately measured fuel consumption chart does the job very nicely, especially with a venerable piece of machinery like a Lehman 120.

An easy way to do it is to plumb a small temporary tank (a 5-gal. white water jog would do nicely) to the engine, and plumb the return line to return unburned fuel to the same temporary tank.  Fill the temporary tank with clean, filtered fuel and mark it in one-tenth gallon increments as you fill.  Then run the engine under load (i.e., underway) for six minutes starting at, say, 1200 RPMs and measure the fuel used at the end of your six-minute run.  Then multiply the fuel used in six minutes times 10 for your GPH rating at 1200 RPM.  Next, go up 100 RPMs and do the same.  Repeat until your engine won't go any faster.  With  much less than a day's labor you'll have a table that tells you exactly what you're burning across the whole range of RPMs--and it'll do so at least as accurately as a flow meter and at a lot less expense.

An easier (though perhaps slightly less accurate) way to go may be to call up Bob or Brian Smith at American Diesel in Kilmarnock and ask them for fuel consumption figures for your Lehman.  http://www.americandieselcorp.com/

I've been using my own home-brew consumption charts on two Grand Bankses, a Nordic Tug and a Nordhavn for the past 20 years or so.  When I finish fueling, I note that I am ALWAYS within five percent of my estimated fuel burn.  Who needs a fuel consumption meter anyway?

Just one way to skin this particular cat.

--Milt Baker, Nordhavn 47 Bluewater, Fort Lauderdale



Chuck wrote:

Looking for recommendations for a fuel flow meter for the single 120 Lehman on our MT34. I am not looking for anything that needs to integrate to my systems or run on my computer. Just a system that will show me the fuel flow under whatever RPMs we are running. Simple is better. Thanks, Chuck