In-line fuel flow monitor

JoeWhite · Nov 26, 2008

I have a 9.9 HP O/B and I get 1/2 Gallon per hour consistently. Of course you must consider the RPM that the engine is running. I usually run it at at about 60 to 75% of max.

Ross · Nov 26, 2008

BrianD, You could make a chart. With some patience and a graduate cylinder run at a GPS speed and record the time it takes to burn 8 ounces of fuel. refill the cylinder and make a run with a 1 knot change in speed and record the time etc.
Remember that increasing your speed also increases your rate of consumption.
The speed/power curves are astonishing as you approach hull speed.

Edit to add: remember if the current is significant run across it but it is best if you choose to run at slack.

Allan12210 · Nov 26, 2008

Here is an analog flow meter I have been evaluating on my salt water cooling flow rate. It has been handy to see restrictions as they develop rather than after the alarms are ringing. This particular one would not be for fuel, it is only for water. You might look around at McMaster-Carr for something rated for organic solvents. It might be pricey. Once you know what is available, scrounge around the industrial surplus stores. I got mine for $12. I get about 2 gallons/minute at idle and around 7 gpm at 3000 rpm (right on Yanmar's spec for the 22GMF). And just in case something were to fail, my strainer is above the water line.

Manny · Nov 26, 2008

Brian, if it helps I think your are real close with the 10% figure. I did some initial testing by using a small tank with 1 gallon of fuel at a specific throttle setting. Then I kept track of my consumption when I moved my boat from PA to MD, the figures worked out to be the same. My 8 HP Honda outboard burns about .82 gph at about 80% throttle pushing a 7000+ lb 27 footer (with a big three blade underneath for the diesel). That throttle setting is the threshold where if throttle was increased, the boat wouldn't go any faster. The real trick to figuring out how much fuel you will need is calculating an average speed for the trip.
Before I made my trip earlier this year I calculated that my average speed would be 5 mph (which was measured on timed runs with and against tides). It turns out I averaged something close to 6.9 mph, even with 20 knot headwinds at one point. Needless to say I had bunch of extra fuel at the end of the trip.

RAD · Nov 27, 2008

I used 1 gph as a benchmark for my 30 hp diesel pushing a 32 ODay for a cruise and ending up with about .5 gph and I have to start logging engine hours starting with a full tank of fuel so I can get an accurate gph for this boat, every season I think about doing it and totally forget about it just making sure I have plenty of fuel

John Nantz · Nov 27, 2008

Allan - that is a really cool setup!

[ref: post #4]

Never thought about doing it that way. Instead I bought a sensor-type device that fits on the incoming water line and when the flow gets down to a certain low amount it sets of an alarm. Installed it several years ago but never connected the alarm!!!

What you did is really thinking outside the box! Good idea.

RichH · Nov 28, 2008

Re: Allan - that is a really cool setup!

What you are looking for is called a 'rotometer' .... slightly conical sight glass with an internal 'float' (similar to what is in Alan's description/pic.). These are available from many instrument and industrial suppliers; the reading is based on the apparent viscosity of the fluid being measured so you need to specify the fluid for a direct read, or do the math from the reading. For fuels, the only caution is that such should be rated compatible for the fuel ... and also consider to get one with a 'hazardous/explosive' rating (which wont be cheap).

The alternative is a 'flow totalizer' a magnetic paddle wheel in a tube which also has an external electronic 'pick up' for a digital readout ... cheaper with hazardous/explosive concerns. Industrial and instrument suppliers have them.

Ross · Nov 28, 2008

Brian D said:
Some good points. Ross, I thought about doing just that, but was going to use a gallon and not 1 cup. But that seems to be a better and easier process. I was also going to do the weight method. I was going to weigh a cup (8 oz) of fuel and weigh the empty container. Then put in some gas, re-weigh, motor for a while and then weigh the container again with the remaining gas in it. That would tell me the amount of fuel consumed in that period of motoring.

Think I'll save a few bucks and do it the old fashion way; slide rule! LOL Thanks guys.

While baking bread this morning, I decided to weigh 1 cup of gas (yeah, I washed my hands). I find that the weight is 6.125 oz. This will equate to 5.8 lbs/gal. Now, all I have to do is weigh my portable tank when it is empty. Cool.

Thanks again and have a great Thanksgiving.

Brian, I am on my second glass of wine but aren't there 16 cups per gallon? Doesn't that make the arithmatic come out 6.125 pounds per gallon? 6.125 ounces times 16 cups divided by 16 ounce per pound equals pounds?

Ross · Nov 28, 2008

Brian , Do you have oatmeal cookies to go with that milk?

Deadhead · Apr 16, 2009

Fuel Flow Monitor

Brain - I found this thread in the archives and am wondering if you installed anything with regards to the inline fuel flow monitor. I am seriously considering installing one for the Yanmar 3YM30 diesel fuel system on my Beneteau 343.

The hitch is that the diesel fuel circulation system has a line from the secondary fuel filter that returns unused fuel to the tank. My feeling is that any flow monitoring system needs to account for this to give an accurate reading for gph consumption.

The system I am looking at is:

http://www.floscan.com/html/blue/seriesdetail.php?sid=1&catid=2

The cost is a whopping $605 plus shipping!

If you haven't done anything you may be interested to know that Consumers Marine has a unit on sale this month for $155.00 that use a single sensor:

http://www.consumersmarine.com/modp...uel_Manager&merchID=3005&str=faria fuel gauge

Regards.
Ted

Taylor · Apr 16, 2009

Lowrance makes a EP-10 sensor and an LMF-200 gauge. Total is about half of Flowscan.

But - my observation has been that a skipper (in this case my dad) can get fixated of the output of a Flowscan. Maybe it was worse on that gas sucking power boat he had, but I don't think it ever told him anything he really wanted to know. At 20 gallons an hour, I think it might have made him miserable. The longer he had the boat, the slower he cruised. Maybe that was a good outcome in the end.

For myself, I recently pumped 90 gallons of diesel into my tank, and measured fuel depth every 10 gallons, and now I have a reasonable way to relate fuel depth to gallons, at least in the top 3/4 of the tank. So now I need to log my hour meter and fuel depth for a while and I should be able to get gallons/hour. From a planning standpoint you need to know the average over time.

EDIT: I don't think a fuel flow device would even work on my diesel, as fuel is constantly pumped through the engine and back into the tank while running. So this is really a gas only question.

tommays · Apr 17, 2009

I have and EP-10 and work on all kinds of flow meters that have to be 99% + good and in general they dont work well at real low flow rates without a calibration done at that flow rate , and 1 GPH is really LOW

And the EP-10 is weak at doing things like running long amounts of time in no wake zones

In-line fuel flow monitor

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