Garmin 315 VHF using Garmin 300 extension cable.

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Hello,

I am changing to a Garmin 315 VHF from a Garmin 300. The 300 had an 8 wire cable installed when the boat was built, running from the saloon bridge to the flying bridge. It would be a nightmare to replace. Unfortunately, the 315 cable has a 12 wire cable, but has a lot of features I do not need on the flying bridge, such as loudhailer, boat speed, position, etc. Nobody can tell me the wire colours for the different services, including Garmin in the US. I am thinking maybe its possible to make a temporary link with 12 wires between the main box in the saloon and the handset and try disconnecting the wires one at a time to see what stops working. Then join up only the essential services using the 8 wire cable. Any comments, please?
 
Ah, the dreaded curly wire insulation failure problem! My sympathies.

Hard to see why it’s not easier to run a new cable or 4 further cores. Definitely would have been possible in the last few boats I owned, even if there were no factory installed conduits (which there were). Are you really sure it’s as bad a job as you think?

If you stick with your plan then it makes plenty of sense. You should find 4 redundant cores (loudhailer, intercom, a pair of n2k, etc
 
Yes. I and my electrician studied the possible routes and they all will be very difficult. The good news was, Garmin replaced the 9 year old radio free of charge. Hats off to them! The plan to use the existing cable would be much simpler if we knew the colour coding of the extension cable wires. Does anybody know a good electronics engineer who might know? Garmin say they do not. Surprise! Surprise!
 
The hailer wires and NMEA 0183 wires are in the power/data harness. N2K is a separate network.

There is a pair of wires for an active speaker, which you might be able to use. Anything else will be trial and error.
 
I've just gone through the pain of replacing my old Garmin with a new Garmin 315. I'd assumed it was plug and play but as you have discovered the cables are completely different. Fortunately, running new cables to the helm wasn't too difficult.
 
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