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Fuel Flow Monitor

2442 Views 9 Replies 7 Participants Last post by  sleeper
I have been doing a little research and would like to consider adding a fuel flow monitor/system to my boat. I have a 2002 310 Sundancer w/ 350 MAG's and v-drives. Standard instrumentation, none of the SmartCraft stuff.

I see there are a number of different options ranging in cost. What are people using out there? How much am I looking at to get this done?

Thanks in advance.
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We currently have a boat with a single I/O. It was interesting the first year I added a fuel flow meter and programed my lowrance to display my MPG while underway. Once i figured out my most efficient rpm I havent really payed attention to it all this year.
It was easy with a lowrance, cut the fuel line, add the flow meter to the NEMA port - Done -
Look at the lowrance stuff. The more common brand (floscan i think) is significantly more expensive.

Lowrance has a whole "lowrancenet" deal. You have to buy a head unit (LMS 200 or 400 depending on size) then you can add whatever sensors you want. Want it to be a GPS speedo? Add the GPS module. I just got the combo with the fuel flow meter, then bought the interface for the fuel sender in the tank, and replaced my fuel gauge with it.

I still use it all the time. My most efficient cruise varies by load and weather conditions, and trim affects it a lot too.

I read my fuel level off of my flow meter. The unit calculates fuel used and fuel remaining based on an integration of the flow rate over time. It's much more accurate than my fuel level sender due to the shape of the tank. That is, it's more accurate unless someone siphons me, then i'm screwed because I wouldn't even know it.
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Garmin has the same devices. But to be honest I'm afraid to look.

The Garmin units work with any of their network able devices (NMEA 2000) and run about $150 each.
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I have installed Floscans on many boats and never had a problem. They are "expensive" because they are very accurate. As an example, when you are making a run for The Canyon out of Cape May NJ you will want to know exactly how much fuel you are using to calculate fishing time. If you load 1000 gallons, you do not want to be 100 or even 1 gallon short on the trip back. The flo scans allow you to adjust your speed on the run.

The installation is not simple in that you are dealing with fuel lines, flow sensors and potential for leaks if not installed properly.
I installed the Lowrance fuel flow sensor along with a depth sounder capable of displaying fuel use. The only thing to remember when installing it is that it must flow UP in order to worlk. I am very happy with it. It senses flow from .3GPH to 17GPH on my 350 I/O.
I have always wondered, but never looked into how you actually calculate what kind of fuel economy you get in a boat. This is very interesting, I am going to have to look into this..........once I have a boat again that is.
My dad has floscans and I have the lowrance unit. Both are off by a similar amount. Both will read up to about 10% high (more flow than you're using)
I guess it depends on the installation, but I have never had flo scans be off by as much as 1 percent. Of course there are different models, so I guess that may be the difference. I would not spend money on any fuel flo sensor that is off 10 percent. I can guess that good.
You can calibrate them to be closer, but there is always a little error. I use mine as a fuel level gauge, as does my dad, and the error that's there is good enough for me. Mine usually reads a little high for flow, so low for gas, and that gives me a small margin of error. My dad's is the same.

But think about the variables you can't measure and can't control. Variances when filling the tank... did it overflow? Did you deduct the exact amount of gas that spilt from what you pumped when you calculated the accuracy? How long has it been since you filled up last? How much evaporated out of the tank in that time, and how much evaporated out of the bowls? I know on both my boat and my dad's, if it sits for more than 2 weeks, the bowls are dry enough that you have to crank it until they're full before it will fire. Did you fill it to the exact same level this time as you did last time?

What about the generator? Did you run your generator, and do you have a fuel flow gauge on that? My dad doesn't... but so far when he's used his generator it hasn't exceeded the "error" in the gauge on the two main engines so his remaining fuel calculation can neglect it.

Since they say you should never use the last 10% in your tank, I think reading 10% extra flow is a good thing, myself!
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