I hate the
thought of sitting down with a logic analyzer trying to decode those
proprietary standards if I ever want to add my own custom hardware the
network again.

Eh, when I'm on the boat I have little desire to hack it. I want it to
operate and not leave me and my passengers in a bad situation. Thus I'm
prepared to live with the way various vendors have chosen to network their
devices. I've got NMEA2k running between my two engines, doing RPM syncing
and transmission control. I "could" bridge that network to my other NMEA2K
network and get at the data. But I'd rather not put something as crucial as
that at any sort of additional risk. I'd feel the same way about anything
actually in control of navigational gear.

I suppose it's both fortunate and unfortunate that they've made the NMEA2k
standard inaccessible. Fortunate that it may serve to keep some junk off
the network (although just because a company could afford the spec doesn't
guarantee...). And unfortunate because it may stifle a bit of low-end
tinkering. But as long as the gear it networks operates reliably, and my
estate can sue the companies if it doesn't, well, that's ok by me.

So I guess I'm suggesting that you give serious consideration to separating
your networks. If you want to tinker then put those devices on their own
network. Put the crucial stuff on it's own network. At least with NMEA2k
(or seatalk for that matter) you've only got a single cable to run.

I'll say this, however, it's my intention before putting it back into the
water to re-rig how the networking runs in our boat. I've had a few
situations where GPS inexplicably went out. No amount of debugging (and
I've really tried) pointed a finger at the culprit. I've gone with adding a
second GPS on a different network (NMEA2k aka SeaTalk2). The boat shipped
with GPS on the SeaTalk network into the chartplotter. But the cabling ran
such that it's not conveniently accessible to allow shunting off
questionably performing devices. So I'll re-route a few of the cables to
let me do it. I'd prefer not to have to do it but it seems like having the
option is the smart thing to do.

You might want to keep that in mind when you're looking at how to route your
cables. Since everything's on a single bus it does help to be able to get
something off the bus in the event it's causing trouble. NMEA2k makes this
easier by using T-connectors. You can simply unscrew a device from the Tee
and the network won't care. Just make sure you've got decent access to all
the Tee connectors and some extra cable to make direct connections should
problems arise.

I've had a sneaking suspicion that the cause of my woes is low voltage. But
when things act up level's still reading a good 12v. But I haven't gone so
far as to add some sort of strip-chart or logging process on a PC to be sure
of it. The problem's so random and infrequent that it hasn't been worth
that much hassle.

-Bill Kearney