NMEA2000

[chrisjrob]

I am looking to upgrade the navigation equipment on my Westerly Merlin.

Existing equipment:

• ST60, for depth and log
• Autohelm 1000 (from memory) tiller autopilot
• Ancient and non-functioning GPS (almost certainly the wiring between GPS and aerial)
• Clipper wind instrument, but the anemometer has flown away

Starting from such a low base, I felt that I should be aspiring to an NMEA 2000 network and, with that in mind, I have purchased a Garmin GPSMAP 750 chartplotter.

I know I can get this working standalone, by following the standard installation instructions, but my temptation is to purchase a Garmin NMEA 2000 Starter Kit and link the GPSMAP 750 into it.

I expect that I can also link in the ST60 log and depth via an NMEA 183 adapter.

I believe I then need to extend the NMEA 2000 backbone up to the top of the mast, purchase an NMEA 2000 wind sensor and a replacement display for the Clipper wind instrument - perhaps a multi-function NMEA 2000 display.

As to routing the NMEA starter kit, my understanding is that the cable can run through the bilges, but only for sections without connectors. I believe I need to route the backbone from the instrument panel, via the switch panel, and then to the foot of the mast ready for extending upwards.

Well those are my thoughts, but I'd be grateful for any advice on whether this actually makes sense.

Thanks!

 

[Cardo]

Just to comment on one point - you likely won't need to run the backbone up the mast. I would hazard a guess a wind instrument will come with a dedicated, long patch cable that will run down the mast and through a deck connector of some sort. This is how my Raymarine unit is set up. I have a SeatalkNG network (which is very similar to a standard NMEA2000 network) and the backbone is very short. Most instruments are connected via adequate length patch cables.

 

[David2452]

Just to comment on one point - you likely won't need to run the backbone up the mast. I would hazard a guess a wind instrument will come with a dedicated, long patch cable that will run down the mast and through a deck connector of some sort. This is how my Raymarine unit is set up. I have a SeatalkNG network (which is very similar to a standard NMEA2000 network) and the backbone is very short. Most instruments are connected via adequate length patch cables.

No the backbone will need to go up the mast as the maximum length allowed for drop cables in true N2K is too short for yacht masts, not a practial issue as it's the same weight of cable, just needs an inline terminator and lightning arrestor both of which come with the Garmin wind instrument. If the Op (or anybody) goes to the Maretron site you can download an N2K design programe that will work out if your proposed design is compliant and produce a parts list and schematic to boot.

 

[Cardo]

No the backbone will need to go up the mast as the maximum length allowed for drop cables in true N2K is too short for yacht masts, not a practial issue as it's the same weight of cable, just needs an inline terminator and lightning arrestor both of which come with the Garmin wind instrument. If the Op (or anybody) goes to the Maretron site you can download an N2K design programe that will work out if your proposed design is compliant and produce a parts list and schematic to boot.

Fair enough. Raymarine do things somewhat differently. My wind instrument has a cable that runs down the mast to a pod that then connects to the backbone.

 

[superheat6k]

I have taken the speed and depth data from my St50 instruments onto my gpsmap750 via a Tri data, which has a built in sea talk converter to nmea0183.

Installing the Nmea2k kit is straightforward. But unless you have more than one instrument up the mast I would treat this as a single take off from the backbone. I would avoid running the backbone through the wet bilge.

 

[knuterikt]

Fair enough. Raymarine do things somewhat differently. My wind instrument has a cable that runs down the mast to a pod that then connects to the backbone.

The Raymarine wind sensor is not a N2K sensor (as opposed to the Garmin wind sensor), the pod converts from the old Raymarine protocol to N2K/SeatlkNG

 

[Ex-SolentBoy]

Backbone is just the same cable as used from the instruments to the backbone. So, taking the backbone up the mast is no big deal. You just need to terminate there as well.

We have a complete N2K network on our boat with stuff from several manufacturers. I really like it. This diagram shows how ours is connected. As long as you create a single line, with a male and female terminator at opposite ends, and tee everything off it you should have no problem.

 

[chrisjrob]

No the backbone will need to go up the mast as the maximum length allowed for drop cables in true N2K is too short for yacht masts, not a practial issue as it's the same weight of cable, just needs an inline terminator and lightning arrestor both of which come with the Garmin wind instrument.

Looking at the price of the Garmin wind instrument, I think I will have to leave that for now. In the meantime, should I be terminating the backbone in a deck plug at the bottom of the mast - is that even possible?

If the Op (or anybody) goes to the Maretron site you can download an N2K design programe that will work out if your proposed design is compliant and produce a parts list and schematic to boot.

Just had a play with Maretron application, struggled a bit tbh, but I will try again this evening, when hopefully I will have more time.

I have taken the speed and depth data from my St50 instruments onto my gpsmap750 via a Tri data, which has a built in sea talk converter to nmea0183.

If you have any more information on this I'd be grateful, as that's exactly what I want to do. I searched for "tri data st50" but found nothing.

As long as you create a single line, with a male and female terminator at opposite ends, and tee everything off it you should have no problem.

That was the impression that I had reached, but it almost seemed too simple!

Thanks all!

Chris.

 

[Ex-SolentBoy]

Looking at the price of the Garmin wind instrument, I think I will have to leave that for now. In the meantime, should I be terminating the backbone in a deck plug at the bottom of the mast - is that even possible?

That was the impression that I had reached, but it almost seemed too simple!

It is simple.

I would terminate inside the boat if I were you. When you add the wind instrument you can extend the backbone through a deck gland so all your connections are inside. Thats exactly what I have

 

[David2452]

Looking at the price of the Garmin wind instrument, I think I will have to leave that for now. In the meantime, should I be terminating the backbone in a deck plug at the bottom of the mast - is that even possible?

Chris.

To remain N2K compliant after fitting the mast instrument I would call that the end of the backbone and use the terminator there below deck, when you get the Garmin wind it will come with a long (very) length of N2K cable with a plug moulded at one end, this goes to an inline terminator which is also included and that connects to the instrument and effectively becomes one end of the backbone. after running the cable down the mast, through a deck gland and cutting to length you use the field attachable plug and lightning arrestor to connect to the backbone after removing the terminator I mentioned ealier. As I said earlier, tall masts make any "Tee" drop cable from the backbone non compliant, that is not to say it will not work in your situation, it also does not mean that it will continue to work after adding other stuff, if you stick to the correct way it will work. The main thing the Maretron programme gives is confidence that your planned install will work as it gives voltage drops at each node and sometimes moving the power insertion point or using another and inserting a power break can make an otherwise dodgy intall a good install and I find it much easier to use the computer first before I get physically involved. I do use it quite a bit so have become familliar with it but it is worth persevering.