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Author Topic:   Convert Mechanically Indicating Fuel Tank Level Gauge to NEMA-2000
RB89BW posted 03-20-2010 06:42 PM ET (US)   Profile for RB89BW   Send Email to RB89BW  
I believe I have a Rochester Dial and sending unit set up on my 1990 Outrage. Do I need to change the sending unit in order to upgrade my fuel gauge to a NEMA 2000 set-up? If not how do I do it? If I do which sending unit is recommended? Thanks RB
jmorgan40 posted 03-21-2010 06:50 AM ET (US)     Profile for jmorgan40  Send Email to jmorgan40     
RB--My first question is which manufacture are you leaning towards? I installed a Lowrance NMEA network and fuel flow module last year on my 20 Outrage. There are two ways you can configure the fuel gauge on the Lowrance network. I opted for the fuel flow meter to calculate the fuel gauge. Option-two is to install an electric sending unit to your current Rochester gauge. The fuel flow meter setup allows me to better trim my setup underway for the best fuel efficiency. You just program your NMEA gauge with the tank size and enter the amount of fuel you add to the tank with every fill-up. You can also choose the recalibrate option every so often. I find it is accurate within less than a gallon with each 25-35 gallon fillup. This thread link has some pics of my setup. Let me know if you have any questions.
SJUAE posted 03-21-2010 03:02 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     
There are many types of Rochester Guages you need to find which one here

Depending on what fuel tank sensor is used will decide if you can attach Fuel Level Converter Kit for a NMEA2000 network, providing if it has the normal 2 electrical connections + and - it should be ok

You don't specify what display or NMEA2000 guage your going to use to display the readings but it must be able to configure and setup the tank capacity etc.

See the reference section which has a 68 page reference manual on the Lowrance 2008 I-Command products for starters.


RB89BW posted 03-21-2010 07:40 PM ET (US)     Profile for RB89BW  Send Email to RB89BW     
Thank you gentleman for getting back to me. I apologize I should have been more specific with my question. Currently I am running a 2006 E-TEC 200 H.O. on my Outrage 22. I already have a NEMA 2000 network started and I also have the I-Command interface set up with my Lowrance HDS-10. Right now I am confused where to connect the wire leads for the NEMA 2000 Lowrance EP-65R fuel level probe cable to my current fuel level sending unit which drives the Rochester Dial? I do not see any leads here at all. Do I need to change the sending unit in order to upgrade my fuel gauge to a NEMA 2000 set-up? If not how do I do it? If I do which sending unit is recommended?

I hope that makes more sense now.

jimh posted 03-21-2010 09:15 PM ET (US)     Profile for jimh  Send Email to jimh     
Your mention of the terms "Rochester Dial" make me believe that your current fuel tank level indicator is a mechanical reading gauge. It is probably linked magnetically to the float sender.

To convert the fuel tank level into something that can be displayed on a NMEA-2000 network you will need to:

--convert the fuel tank level float and sender to an electrical sender

--use a tank level sensor convertor to connect to the new electrical sender and convert the electrical signal to a NMEA-2000 network parameter, such as the Lowrance EP-65R

--calibrate the tank level using the software provided with the sensor or the NEMA-2000 display controlling the sensor.

There is a de facto standard for fuel tank level sensors using a rheostat. I believe the resistance range is typically 35 to 240 ohms. You have many choices for how to replace the existing mechanical sensor with an electrical one.

The simplest is probably to use the Rochester Gauge electrical sender option. In the REFERENCE section there is an article about Rochester Gauge senders:

The article links to this Rochester Gauge catalogue page:

This will show you the Twin-Site electrical sender, part number, and specifications.

There is also a very interesting and thorough prior discussion on the topic of electrical fuel gauge senders in the archives of SMALL BOAT ELECTRICAL; see:

Fuel Gauge Sender: Electrical

jimh posted 03-21-2010 09:24 PM ET (US)     Profile for jimh  Send Email to jimh     
I have not tried to replace the mechanical Rochester fuel gauge with an electrical sender. In doing so, I would anticipate two problems:

--the bolt hole pattern used by the Rochester gauge appears to be in conflict with the normal SAE five hole pattern used in many other gauge senders;

--the height of the Twin Site electrical sender may be too great to fit under the cockpit deck plate on a Boston Whaler.

If you change the sender on your Boston Whaler to an electrical unit from the standard Rochester Gauge mechanical dial with magnetic linkage to the float, please let me know if you encountered these problems, and how you overcame them.

jimh posted 03-21-2010 09:28 PM ET (US)     Profile for jimh  Send Email to jimh     
One of the reasons why I have not undertaken a conversion of the mechanical fuel tank level gauge on my Boston Whaler boat (a 22-foot REVENGE) is due to the wonderful simplicity and reliability of the existing mechanical gauge. It just works well, and I can't see the advantage of making it an electrical gauge.

I also track the fuel tank level indirectly using a fuel flow measuring transducer and associated fuel flow instrumentation. Actually, I have two of these systems: a NAVMAN 3100 FUEL instrument with its own in-line fuel flow sensor, and the built-in fuel flow data from my E-TEC engine. You might say I have three fuel tank level gauges. The one to which I give the most authority is the OEM Rochester mechanical gauge. If it says "E" I head for the fuel dock.

RB89BW posted 03-23-2010 05:17 PM ET (US)     Profile for RB89BW  Send Email to RB89BW     
Thanks for the info. I will look into the resources you supplied me with. Some of the issues you make I was already anticipating. After researching a little more I will make a decision on what I want to do. Thank to all your help is greatly appreciated.

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