350 - NMEA backbone upgrade

NMEA backbone upgrade

Printed From: myHanse.com
Category: Hints & Tips
Forum Name: 350
Forum Description: 350 Hints and Tips
URL: https://www.myhanse.com/forum_posts.asp?TID=15079
Printed Date: 27 March 2026 at 01:44
Software Version: Web Wiz Forums 12.06 - https://www.webwizforums.com

Topic: NMEA backbone upgrade

Posted By: Mark Pullen
Subject: NMEA backbone upgrade
Date Posted: 29 April 2025 at 13:49

Hi, I am considering updating the navigation systems wiring to a modern NMEA 2000 backbone. My 350 has the original Simrad CE33, AC12, then newer AP40 display and IS42 displays. Log and wind cables are currently connected into the old IS12 (which is under the coaming), which is connected to a new IS42 via a Simnet to NMEA conversion connector.

Has anyone updated their backbone to NMEA 2000? If so, all advice welcome. What was your approach, what were the challenges, could Simnet cables be retained and what else did you upgrade? For instance, I am keen to upgrade the chart plotter to a basic, but new model.

Many thanks, Mark

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Mark

Replies:

Posted By: PekkaL
Date Posted: 29 April 2025 at 14:30

Simnet is NMEA2000 with proprietary connectors. Adapter cables, with Simnet connector on one and NMEA2k connector on the other end, are available to connect the two (about €50/piece).

Note that the adapter cable's NMEA2k Micro-C end has two alternatives: male or female connector. Choose the right version based on what you are connecting: adding a NMEA2k device to Simnet T-piece, or connecting Simnet backbone to NMEA2k backbone.

In the cockpit pinnacle I've kept Simnet, connecting new NMEA2k devices with an adapter cable, mainly because I have spare Simnet to NMEA2k adapter cables for this purpose.

In the main cabin installation cabinet I've used an adapter cable to add a NMEA2k segment to the end of the backbone in order to use the standard NMEA2k cables/connectors.

So I have a hybrid: Simnet backwards from the installation cabinet and NMEAS2k on the other side of the cabinet. I still have a Simnet cable running from the cabinet to the pinnacle, as I see no point in changing this & do not know if I could pull NMEA2k connectors through the connecting pipe.

The standard NMEA2k cables lock more strongly (push and then twist to lock) to the NMEA2k T-pieces than the Simnet ones to their T-pieces (push only), but I've never had an issue with the Simnet ones.

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Pekka Leppanen, "Vedette"

Posted By: asimo
Date Posted: 10 June 2025 at 10:02

Mark,

Im going thru a similar issue at present (hence why i saw your post on this forum). After lots of discussion with vendors and knowledgeable people, i have come out with the following:

1/ simnet to micro c cables and adaptors appear to be diminishing in availability.

2/ you need simnet to micro c cables to fit NMEA 2000 gear (B&G for example) to the proprietary simnet backbone. Make sure you know whether you need micro c female or male fitting.

3/ changing the simnet cable/backbone out for Micro C is big and possibly expensive decision to make. you need someone who knows what they're doing to look and advise.

4/ i inherited a heap of simnet cables, fittings and B&G gear. so im going to keep the simnet backbone and just use adaptor cables to join into simnet.

5/ I have not considered Raymarine. I believe they use their own cables too.

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H400e - DE HANJ0344K708

Posted By: Mark Pullen
Date Posted: 10 June 2025 at 12:10

Yes, it's a real dilemma. We have adaptors at present. However, I recently needed to replace one of the Simnet multi joiner blocks because it was old and the connections corroded. I'm concerned that the old wiring will eventually give up. I'm on the boat shortly and will try to map out the connections, to assess how/whether to replace with NMEA2k connectors.

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Mark

Posted By: Snublefot
Date Posted: 14 July 2025 at 23:06

I have upgraded to Raymarine instruments, sensors, autopilot and plotters. All The backbone and cables are changed to Raymarine NMEA 2000 (Seatalk ng).

The biggest job was to find how to Get The cables to the instrument locker from instruments, pidestal, mast, transducers and companionway.

If you need some tips, please let me know and I will try to help.

Posted By: Ian Coverdale
Date Posted: 15 July 2025 at 08:43

SIMNET uses exactly same NMEA2000 'approved' cable as all the other NMEA2000 systems, as already said, it is just the connectors that are different.

I cut some SIMNET connectors off then soldered on Micro-C connectors where network has been extended for new/upgraded instruments. A lot easier and cheaper than trying to run new cables through the boat.

Solder-on connectors were ~£4 ($3?). They are available as screw-terminals but personally I'd not trust those.

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Ian & Andrea
SV Gabrielle (H445)
Liveaboards - currently Montenegro.
www.facebook.com/sailinggabrielle

Posted By: Sjakk
Date Posted: 17 August 2025 at 22:15

I am doing a similar job, integrating an axiom plotter.

How did you pull the backbone cable down the pedestal?

I have a Hanse 400 from 2006.

Mvh

Lasse

Posted By: Brufan
Date Posted: 18 August 2025 at 18:31

Very easy.
Unscrew the top pod on pedestal (4 allen screws on the side) Slide the pod up (a bit tricky with handle bar but doable) then you will see how existing cables are routed. just follow the path. Avoid to run cable too close from wheel quadrant, route the cable down and catch it below (usually in autopilot "locker"), the cable will "enter" in the aft lazarette.
Quicker said than done but not complicated

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Bruno

hanse 355 - 57

S/Y Spicy Ginger

White hull, 2 cabins, Volvo D1-30, Selden rig, removable mainsheet track system, Simrad (now B&G)-Jefa autopilot.