Gas tank gauge

MarkB

I recently had a mercruiser smart gauge installed on my boat. I got the boat back yesterday and have found my gas tank level gauge is to reading at all. The level shows on the digital display of the smart gauge. It looks like the mechanic severed the connection to the older gauge. Is there any reason the two cant be off yea same sending unit? I'd like to have the gauge working

raybo3

I am not sure at all about this but my guess is the resistance in the old gauge could cause a problem on the smart gauge. Again its just my thought and I have never worked on the smart gauge system. Please keep us posted.

MarkB

Sorry there's a typo in my original post, for some reason I can't edit.

 

Anyhow, my Faria gauge is not reading tank level at all.  The mechanic had to put on a special harness on the fuel sending unit to get the smart gauge to pick up level.  I can see the old harness is disconnected, so I'm guessing this severed the comms to the Faria gauge.  Can the live/neutral be spliced to the Faria gauge so I get readings on both the Faria and Mercruiser Smart gauges? Or will this mess the one up with the other?

From what you write Raybo perhaps yes it is a problem, not sure.  I don't think they changed the fuel sending unit, so the output should still be standard for both gauges. I'm guessing if the output is the same, the resistance at the gauge would be the same.  Anyhow, now I am clearly starting to guess...

mvn

Not familiar with the system but from a sensor perspective,  if excitation voltages are different,  calibrations will be different therefore two display devices cannot be connected in parallel if they expecting different signals.   Now,  maybe they can work together.   With some electronics,  it may be possible to have both behave.   If no one can answer your question,  I'll dig into this a bit when I get a chance. 

Mark

mvn

OK.  Dug into this a little.  Fuel sending units control the amount of current going to the gauge.  Looks like standard resistance specs are 33 ohms to 240 ohms.  Now for a dual station setup, the fuel sending unit gets changed out to one with half the resistance ie. 16 to 120 ohms.  This provides twice the current to drive 2 gauges.  In your case, we're talking about one gauge and one digital readout.  I'll see if I can figure out how the Smart Gauge stuff works and get back to you.  The key is to figure out how much current the Smart Gauge is using.

Mark

MarkB

Thanks Mark..

mvn

Exactly which model of Smartcraft gauge are you using?

MarkB

There's only two for the mag 359. I have the analog dial for rpm and a digital screen at bottom, with smart troll buttons on either side at very bottom.

Michael T

Hey Mark, I would advise extreme caution when crossing the different systems. My new boat has DTS, Axius and SmartCraft (Vesselview). We had Mercury techs link my Garmin GPS to the VHF (for auto DSC and GPS auto emergency distress hailing) and the GPS to the Smart Craft for auto pilot. Here's some of what you get into. Writing sentence code for NMEA 0183 and NMEA 2000. Mercury Can Backbones and Garmin Smart cables and Backbones and relay switches to enable drift alarms. Everything was done strictly by the book with multiple calls at each stage to factory techs of all units.Different impedences and bandwidth language (BAUD). It is a very new world. Bless them, the techs are having a heck of a time keeping up with the advances. I have learned one thing for dead sure. When in doubt with these systems do not cut or connect a wire unless you are darn sure what you are doing or you start to smoke systems. Be very careful my friend!

mvn

I fully agree with Michael T. You have to be very careful, especially in this case since we're dealing with analog signals, not digital data streams. I've been too busy lately to further investigate the Smartcraft input signal requirements but I'll get to it at some point.

Mark