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The LMF-400 gets its power from the NMEA 2K buss, the four additional wires coming from the LMF-400 are two for dash lights and two for piezo alarm.
I ran my NMEA 2K power from the engine ignition power so the LMF-400 only comes on when I start up the engine/engines. I ran my dash light power to the LMF-400 from the existing dash light circuits so all the dash lights come on when you turn up your running lights.
Some folks run the NMEA 2K power from the electronics switch on the house battery so the NMEA 2K network is on anytime the house battery and electronics/accessory switch is turned on. Some have run the NMEA 2K power right to the battery switch so the NMEA 2K network is on anytime the battery switch is turned up.
Pick a power source and run time that works for you. I think most connect the NMEA 2K power to the engine ignition power.
Thanks Jim. The lowrance documentation is confusing at best.
So only power source can be connected to ignition. I def plan to connect backlight to anchor/nav light switch.
Do you know if the LGC 3000 will also display gps position on the 400 or just be used in cumputation for MPG, etc.
I read some conflicting stuff on this (from way ****** when searching old threads here.
Thanks again.
The LGC3000 puts the GPS data onto the bus and ANY and ALL devices that connect to the NMEA2000 bus can use the data. That's one of the beauties of the NMEA2000 bus.
I would not power the LMF from the ignition power. Your exposing the unit to voltage drops at engine start. This may/will cause unit resets. Power LMF from an aux switch on your dash. then turn unit on after you start the engine. That way you can also adjust unit without running the engine. Connect the light circuit to existing dash lights.
I take the power right off the key switch and it works just fine. No problem at start up. This is how Evinrude does it with their special trim/tilt cables for I-Command. I just used my old cables and wired up the ignition feed myself rather than using the new cables.
The gauges have fuel management options. It's sometimes convenient to be able to use them without having the engines running. That's why I have mine connected to the same breaker that controls the chart plotter, and not the engine ignition circuit. I wouldn't use a fuse, I'd use a breaker. That way you can use it to turn them off/on if necessary (like a reboot due to software issues or something).
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-Bill Kearney, 34' Four Winns 348 Vista
The gauges have fuel management options. It's sometimes convenient to be able to use them without having the engines running. That's why I have mine connected to the same breaker that controls the chart plotter, and not the engine ignition circuit. I wouldn't use a fuse, I'd use a breaker. That way you can use it to turn them off/on if necessary (like a reboot due to software issues or something).
This may be the route I go if I can figure out how to use them on the same breaker.
You can always have both worlds, you can use a pair of diodes and have the gauges come on with the ignition, or by turning on a switch/breaker.
Most NMEA 2K busses are fused as the power supply turns up everything on the buss, fuses are faster than breakers, so take your pick, either will work.
My buss I believe has a 2 or 3 amp fuse, it is hard to find a 2 or 3 amp breaker. Not a good idea to go to 5 amp breaker.
Good point about 2 to 3 amp vs a breaker. I'd have to look at what the Lowrance docs recommend. I'd probably use a fuse in-between the gear and a breaker. If it's truly a low draw then there's the possibility of tying into an existing circuit. That way you'd get the quicker, lower amperage coverage of the fuse and the convenience of the breaker for toggling the power.
Not sure about the diode idea, mainly due to the voltage fluctuation that's likely to occur on the starting circuit. The digital stuff tends to be a bit more picky about reliable and steady power. You really don't want uneven powering of the network devices. I had a devil of a time narrowing down some troubles with mine. Going with a heavier, direct wire for my chart plotter eliminated the voltage drop. Getting all the SeaTalk and NMEA stuff on that same circuit took care of the rest.
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-Bill Kearney, 34' Four Winns 348 Vista
NMEA 2000 BUS Install (LMF-400)
