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Author Topic:   Logging Fuel Used with Lowrance HDS-7 and Yamaha F70
DVollrath posted 09-28-2012 05:14 PM ET (US)   Profile for DVollrath   Send Email to DVollrath  
I would like to be able to log the amount of fuel consumed over time using my Lowrance HDS-7, which is connected to my Yamaha F70 purchased new in 2011. I am able to read instantaneous fuel consumption from the engine, which the HDS-7 utilizes along with the GPSr speed to calculate and display fuel economy. This works great. The HDS-7 manual does list steps for enabling fuel consumption logging, which I believe I have followed, but "Fuel Used" is always 0. I think I have done things right, but with me there is always a chance of operator error.

Jim--the link and documents [probably means my article on NMEA-2000 instruments--jimh] you pointed me to are very good. Thanks. I'm not clear that lack of a network data storage module is the problem here though. The context there seems to be ICOM gauges [actually I talk about ICON gauges, made by Evinrude--jimh], which as you point out have no persistent internal storage [actually ICON gagues have their own data storage and retain it with power shut off--jimh]. The manual for the EP85 notes this as well. The HDS-7 has persistent internal data e.g. waypoints, routes, trails, etc., the HDS-7 manual makes no mention of any network based data store requirement, and so I am a bit skeptical that this is the crux of the problem.

I called Lowrance support, which has been very helpful in the past. After some off-line consultation, the operator said that Yamaha did not support this function and that I would need to purchase a fuel flow sensor or level sensor. In this instance, I came away unsatisfied, as I believe the Yamaha engine is already sending the same data a fuel flow sensor would, that is instantaneous fuel rate at some point in time.

I assume the HDS-7 is polling the devices on the NMEA-2000 bus at certain intervals, or perhaps it is interrupt driven. However it is accomplished, the HDS-7 is receiving a fuel rate value, and has a time interval value available, so it should be able to internally determine fuel consumed in each interval and sum them all together into the amount of fuel used. It is pretty basic stuff, and I'm surprised the unit does not do it.
Long intro to my question, but has anyone else successfully gotten a Fuel Used value to be displayed on a Lowrance HDS unit when just connected to a Yamaha motor via NMEA 2000 network? If so, any tips?


jimh posted 09-28-2012 08:18 PM ET (US)     Profile for jimh  Send Email to jimh     
Dennis--ICON gauges have their own storage for data. (ICOM have made some gauges but they are very obscure and not discussed in my article.) BRP's ICON gauges operate entirely independent of the HDS FUEL MANAGER.

If you want an HDS device to track fuel usage, you need an EP-85R Data Storage Device. Add one to your NMEA-200o network and you will get data about fuel consumption.

|I don't know about Yamaha engines. If they are sending data on fuel flow rate that is used to calculate the instantaneous MPG, then that data can be used to calculate fuel used by the HDS FUEL MANAGER.

jimh posted 09-29-2012 10:02 AM ET (US)     Profile for jimh  Send Email to jimh     
The HDS series of devices does have some storage for data such as waypoints, routes, and trails, and off course for the myriad of settings applied to it, but it does not have storage for the FUEL MANAGER data such as fuel tank level. This is probably because it is intended to interoperate with Lowrances LMF series of gauges. The LMF series does not have storage for data like fuel tank level, and Lowrance developed the EP-85R Data Storage Device as the method to hold the data about fuel used. It would cause problems for Lowrance users if the LMF gauges worked differently from the HDS display, so I assume they made them all work the same way.

If an engine (such as the Yamaha) is NMEA-2000 certified, then I presume it sends the NMEA-2000 parameter group about dynamic engine data. I explain these parameters in detail in a separate article. See

The common PGN for engine data includes fuel flow, ergo the Yamaha engine must be sending the fuel flow rate. You are getting a calculation for MPG based on the data from the engine on fuel flow rate, ergo this tends to confirm the Yamaha is sending the fuel flow rate data on the network. This is the same fuel flow data that will be used to compute fuel used.

I cannot say with certainty that the HDS will accumulate fuel flow with your Yamaha engine, but I cannot see any reason why it would not. You might try probing more deeply into Lowrance customer support to see if they can tell you why they think the Yamaha engine can't function with their device. The two devices are NMEA-2000, so you'd expect they would work together.

jimh posted 09-29-2012 10:09 AM ET (US)     Profile for jimh  Send Email to jimh     
I agree that the general method for integrating the fuel flow rate over time into a value for fuel volume will involve some sort of periodic sampling of the rate at fixed time intervals. The result will be a calculated fuel volume. I do not know the details of the method used by the HDS series.

At the moment on my installation I have two devices calculating the volume of fuel flow. I presume they both use the same technique. They apparently use a slightly different time interval, as the calculated fuel flow volume is not precisely the same on the two devices. After about 50-gallons of fuel flow there will be a small difference in the computed fuel flow volume. I attribute that difference to a slight difference in the time intervals being used, or to some other difference in the computation method. But the variance is very small, perhaps a few tenths of a gallon over a volume of 50 to 100 gallons of fuel.

DVollrath posted 09-29-2012 02:39 PM ET (US)     Profile for DVollrath  Send Email to DVollrath     
Perhaps this is just a matter of the difference between the way things work, and the way I want them to be.

The HDS unit has all of the data, computational power, and storage to calculate the "fuel used" on its own. It should just be a matter of software development, if it does not currently work this way.

I was mistaken in asserting the ICOM gauges [actually I talk about ICON gauges, made by Evinrude--jimh] did not have storage. I did mean LMF gauges. From the Lowrance website: EP-85R-Storage-Device-en-us.aspx

There is a warning:

Can only be configured and used by Navico MFDs and LMF gauges

This leads me to suspect you are right about the development history influencing the capabilities they build into newer products, as I assume LMF was introduced before HDS.

I do plan on pressing Lowrance support again, if nothing else than to suggest they modify a future software release to include this, if possible.

I won't shell out $80+ for the EP-85R for this boat, when the tank handle is so close.

Great information. Thanks for the discussion.


jimh posted 09-29-2012 02:52 PM ET (US)     Profile for jimh  Send Email to jimh     
The method used by Lowrance in which they store certain data in a memory module does seem a bit awkward at first glance. I have given some thought to why they used that approach. I concluded that perhaps keeping the data in one place, in the external storage device, allows many devices to access the data. For example, the fuel tank level data can be shown on several devices. You could have a dedicated electronic NMEA-2000 gauge just for fuel tank level. You could wish to also display the level on a multi-function screen like a HDS unit. Or you could have another gauge that was programmed to step through various data and shows the fuel tank level periodically to the operator. If the fuel tank level data were stored locally on a device, it might be more difficult for other devices to share that data. You'd have to configure this all manually. I think Lowrance sets up their instruments so they look for the EP-85R External Data Storage device as the source. This makes their set up more plug-and-play and allows it to work with a variety of their gauges and multi-function displays.
jimh posted 09-29-2012 03:30 PM ET (US)     Profile for jimh  Send Email to jimh     
Dennis--You write "ICOM" but I think you mean ICON, the gauges made by BRP.
newt posted 09-30-2012 07:50 PM ET (US)     Profile for newt  Send Email to newt     
I have a Lowrance LMF 200 installed on my boat in conjunction with a pair of fuel flow sensors. I do not have a network storage device installed. The LMF 200 retains fuel manager data such as tank level and trip data without an EP-85R.

newt posted 09-30-2012 07:57 PM ET (US)     Profile for newt  Send Email to newt     
Perhaps in my configuration, the fuel usage is stored in the fuel flow sensors, as apposed to the LMF gauge?
jimh posted 09-30-2012 08:02 PM ET (US)     Profile for jimh  Send Email to jimh     
Newt--thanks for the information on your set up with Lowrance instruments. Your speculation sounds correct to me. That data has to be stored someplace on the network. I have never used a Lowrance flow sensor on my network, so I am not familiar with them.
jimh posted 10-02-2012 01:32 PM ET (US)     Profile for jimh  Send Email to jimh     
Dennis--Try this suggestion: beg or borrow an EP-85r from a dealer or even from a fellow boater. See if it solves the problem of accumulating fuel used. It is near the end of the boating season, so perhaps someone you know has hauled their boat and would lend you an EP-85r
DVollrath posted 04-15-2013 10:04 AM ET (US)     Profile for DVollrath  Send Email to DVollrath     
I ended up getting one of the EP-85R modules. I'm not sure how I can justify the expense versus the "lift the tank" method, but that's the geek in me.

Sees to work fine. The only drawback is I need to configure the vessel as 1 engine & 1 tank. The 1 engine 2 tank configuration seemed to draw from both simultaneously, and some of the web lore indicated this was other's experience as well. At any rate, I'll report back with my experiences as I get more history with the setup.


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