Connecting Lowrance chartplotter to Cobra MRF55 vhf

[Superaquarama]

Can anyone help with this ? The cable from the Lowrance has 3 wires - red, yellow & black.

The connection to the radio is via a simple mono jack plug which will have 2 wires coming from it.

I just need to know which colour wires go to the jack plug, and also which way round they go, i.e. what colour goes to the pin and what to the outer. And what happens to the spare wire - presumably not used ?

Thanks,

Anthony

 

[prv]

Which Lowrance plotter?

The manual for the VHF unfortunately only describes the connections in terms of the wire colours from their supplied plug - presumably you don't have this plug available? My guess would be data on the tip, ground on the sleeve, but if that doesn't work just try swapping them over, a reversed connection should not cause any damage.

Once you enlighten us as to the plotter model, we can read that manual for you too to find out which colour is the output data and which is the ground.

Pete

 

[Superaquarama]

Thanks, Pete.

No, I don't have the original jack plug, the radio came with the boat. The Lowrance model is a Mk 4 chartplotter / fishfinder. I have the manual for this but it just refers you to the vhf manual, understandable I suppose as presumably radios may differ as to their connections.

Actually, reading the Cobra manual again it says:

Bond the NMEA out negative wire to the black wire of the GPS cable
Bond the NMEA out positive wire to the red wire of the GPS cable

If it's safe to assume that the tip of the jack plug is + ve, would you agree that this seems to give the answer ? And the yellow from the GPS is just ignored ?

 

[prv]

Actually, reading the Cobra manual again it says:

Bond the NMEA out negative wire to the black wire of the GPS cable
Bond the NMEA out positive wire to the red wire of the GPS cable

If it's safe to assume that the tip of the jack plug is + ve, would you agree that this seems to give the answer ? And the yellow from the GPS is just ignored ?

No, because Cobra don't know what GPS you're going to connect it to, do they?

Those colours refer to the wires coming out of the Cobra plug that you don't have, so they're not very much help.

Give me a minute to check out the plotter manual...

EDIT: Ok, the Lowrance manuals are pretty poor, don't blame you for struggling with them . If I've understood correctly, the yellow wire is the NMEA out channel; the black one will be ground for both channels. So, provided my guess about the Cobra plug is correct, you want yellow to the tip and black to the sleeve. The red/orange wire I believe is an NMEA input channel, which you don't need for this installation - just tape it up.

Pete

 

[bitbaltic]

NMEA in is indeed in the tip of the plug for the cobra and ground in the sleeve. Make sure you are using a 2.5mm plug and plugging it into the correct socket on the cobra. There is a 3.5mm mono socket on the back which some versions of the manual indicate is the NMEA in. It isn't it is the ext speaker out. This had confused a previous owner of my boat and it took me a surprisingly long time to work out why neither the NMEA feed nor cockpit speaker worked as he had them the wrong way round.

Cheers

 

[Superaquarama]

Thanks for the further help, both.

I connected up the Lowrance to the Cobra this afternoon, but unfortunately no joy.

I have the yellow from the GPS to the centre pin of the jack plug and the black to the outer of the plug (yes, it is the 2.5mm one, my radio seems to have 'em the right way round !).

Presumably the radio should now display the lat. & long as per the GPS, but all we have is a series of 9s.

Any further thoughts ? Presumably all 2.5mm jacks are the same and I can't be using one that's too short or something ?

Postscript: I just checked the NMEA output 'sentences' on the GPS and all the various boxes are ticked, which I assume is the default setting & how it should be. Also, the GPS installation manual refers to yellow being the tx and black being ground, which seems to confirm what we thought, although it doesn't mention the red wire.

 

[bitbaltic]

Thanks for the further help, both.

I connected up the Lowrance to the Cobra this afternoon, but unfortunately no joy.

I have the yellow from the GPS to the centre pin of the jack plug and the black to the outer of the plug (yes, it is the 2.5mm one, my radio seems to have 'em the right way round !).

Presumably the radio should now display the lat. & long as per the GPS, but all we have is a series of 9s.

Any further thoughts ? Presumably all 2.5mm jacks are the same and I can't be using one that's too short or something ?

Postscript: I just checked the NMEA output 'sentences' on the GPS and all the various boxes are ticked, which I assume is the default setting & how it should be. Also, the GPS installation manual refers to yellow being the tx and black being ground, which seems to confirm what we thought, although it doesn't mention the red wire.

All I'd suggest is swapping the yellow for the red if it isn't working. But that is based on no knowledge of the lowrance whatsoever. But in most NMEA installations the red is the Tx and the black the ground. Sorry, can't be more help than that, although I think it unlikely you will fry the radio if you try.

Cheers

 

[prv]

in most NMEA installations the red is the Tx

That's not been my experience at all, I'm afraid, and I had quite a number of connections to make between Ariam's wide menagerie of instruments. Blue and green seemed quite popular, but also brown, grey, pink, and probably others. There really is no standard.

I agree that black is quite commonly (but far from universally) the ground, and that experimenting will not harm anything.

Pete

 

[Superaquarama]

Further developments Just for the forum record, really, as I'm no further forward.

Got hold of Lowrance / Navico tech support today and was advised that their NMEA 0183 cables sometimes have some tiny components added at the end of the cable, sheathed in shrink-wrap. Just a tiny resistor and what looks like a diode.

They said to cut this off as it's not needed for 99% of radios, then ensure the yellow goes to the centre pin of the radio's jack plug and the outer sheathing to the outer/ground of the plug.

Did this, but no change whatsoever ! So still on the case, will report back if I have any success.