Mystery electrical system problem - not sure how to proceed.

[AstoriaDave]

Sunbeam wrote:
Okay, so if all the wiring on the "other" side of my equation is #6… that seems like it is plenty good for a larger-than-30-amp fuse. But….I only have 10 gauge running from the positive bus up to the helm panel (and that is wire that came with the boat, so probably nothing special in the quality department). However now I'm getting confused Embarassed I now think I know that all the individual fuses (mentioned in my list) protect the "small" wires running from the components to the fuse block (behind the helm), or the switches (by the helm). But does the 30 amp main fuse protect the "other" wires "behind" it (house battery/ACR/Safety Hub/main switch in lazarette, all #6 wire), OR does it protect that "supply" wire running from the positive bus to the helm area? I should be able to figure this out but…. maybe my brain has too small a fuse tonight

Diagram this all out and it will make more sense. Sounds like the fuse should protect just the run from the battery TO the buss bar/fuse block behind the helm, #6 all the way, yes? Other runs off the same battery terminal, perhaps passing through a switch, should have their own fuses, if that is what you are describing. I don't know what loads you can expect to those other items, so wire size and fuse will need to be selected accordingly.

 

[hardee]

Hi Sunbeam,

Sorry to hear about the electrical challenges. I am not boating electrician like some of the respondents are but, I would bet on the 12v cigar lighter plug. It is not uncommon for them to do a direct short when plugging or unplugging a device. I have seen them heat up to the point of melting things around -- and found that due to the smell of hot plastic.

These plugs do come in 2 (that I know of) different diameters. Some plugs are too large to insert, if it is the smaller size, but if it is the larger one, they will all fit, just not snug, as you have found.

That was a pretty cool full moon rise. I watched it come up over Whidbey and light across the PT bay and the forming fog.

Sounds like you have your electrical outage in hand.

Harvey
SleepyC:moon

 

[AK Angler]

OK, Sunbeam (and others following this thread)... I've got a correction to make to my earlier posts regarding wire/fuse size amperage limits. (I DID say I was digging those numbers out of my memory... )

According to this wire/fuse sizing chart available on the BlueSeas website, 10ga wire (that's bundled with other wires) can be adequately protected by a 40A MIDI/AMI fuse. So, if you find the fuse is popping because you simply have too much load for the 30A MIDI/AMI fuse, according to Blue Seas you can safely bump it up to a 40A MIDI/AMI fuse with your 10ga wire.

However (and not really related to your current fuse blowing problem), that same chart indicates that a 30-foot run of 10ga wire (positive and negative combined length) can only handle a 10-amp load before getting voltage drops greater than 3% (can screw with electronics), and up to 30-amp loads before getting voltage drops greater than 10% (bad for even "non-critical" loads). To handle 40 amps of current without voltage drop issues, you might be able to get away with 8ga wire, but 6ga would definitely be better. This may be why your installer opted for a 30A fuse, instead of the max-capacity 40A unit.

That being said, at some point you should add up any/all loads that may ever be used at the same time and see what your actual maximum load on that circuit is. You can use the fuse sizes in the distribution block at the helm, but that will over estimate the actual numbers. For instance, the wire to a wiper motor that draws 2 amps may be protected by a 5-amp fuse. So, it would be better to use the actual loads of your devices - if you can find them. Don't include any combinations that you know you will never use - like maybe the washdown pump and the trim tabs, or the autopilot and a windlass.

Then, when you're confident that you have a realistic upper end for the load, you can take a look at the wire/fuse size chart and make a determination if you need to upgrade. And, I would use the 3% voltage drop chart, because some electronic components are voltage sensitive, and we're talking about the main house feed. Besides, at some point you may want to add another gizmo or gadget, and it'll be nice to have a bit of "extra" electrical capacity.

 

[jerry97230]

Fuse holders can be bad, not making a solid ocnnection with the fuse and there for heating the fuse and causing it to blow.
If everything is fused, the little fuse should blow first. So either the total load is to large or there is a short in the ciruit before the smaller fuses, or there is something wrong with the main fuse holder.
Jerry C Nile C22

 

[Sunbeam]

Good morning all,

Your new posts have clarified about which wires are being protected, by what - thanks!

So we did some thinking and figuring this morning (before logging in here).

I found a West Marine chart for both 10% and 3% voltage drop. From what I (now) understand, 10% voltage drop is adequate for protecting some wires (i.e. so they won't catch on fire). 3% is best for equipment functioning (and also recommended for some important "smaller" loads such as running lights, etc.)

So, I figured my up & back run to be about 28'. Based on that, 10 gauge wire (which I have at the moment) is fine with a 30 amp fuse. So therefore (if my new and tenuous understanding holds here), the current wire running up to the helm and back, and the 30 amp main fuse are compatible. Perhaps this is why the 30 amp main fuse was chosen in the first place (not by me then, but now I am learning :thup).

Then I wrote down loads for the current equipment, plus added some things I may install. To figure out what wire size would be best to upgrade to (after which I could see what size main fuse would safely protect it). Here is what I came up with (some equipment didn't list a draw, so I had to go by what fuse size they recommended - realizing draw is probably less).


Basic instrumentation now, all on = 2.5 amps

Future radar = 3.0 amps

Two (one future) 12 volt outlets = 18 amps (yes they are rated for more, but I'm trying to be somewhat "real world" and, for example, my computer charging and in use with full screen brightness and inverter is 5.0).

Future Autopilot 0.0 (would be mounted in laz); (current autopilot not listed in specs, and I'm not even sure it's working, so not counting for now).

Future wipers, two AFI 1000 5.0 for both, estimated.

Cockpit spotlight = 3.0 amps

VHF transmit = 5.0 amps

Fan (plus future second fan) = .5 total for both

Washdown pump (if have switch forward) = 6 amps

Cabin lights = would use LED so not counting for now (current two draw 3 amps total, but I don't use them).

Bilge pump manual switches, if both running via those switches = 2.2

Nav lights = .37 (although would be more if LED lights stopped functioning and I had to put in spare incandescent bulbs; but I'm ignoring that for now because if that happened I could consciously reduce other draws).

Horn = 5.0

Scenario #1 All together (including equipment I don't have yet) is around 50 amps

Scenario #2 Removing 18 amps somewhat arbitrarily (say VHF and washdown pump and bilge pump manual switches and horn not used together, etc.) = 32 amps.

Other draws on boat don't run through helm area (e.g. trim tabs). Future windlass would have its own wiring.

So:

28' run, 10% drop, 50 amps = 8 gauge wire.

28' run, 3% drop, 50 amps = Just on border between 4 gauge and 2 gauge.

Scenario #2, for 32 amps (probably more realistic, I'm thinking, given my overall use and system size):

28' run, 10% drop, 32 amps = 10 gauge
28' run, 3% drop, 32 amps = 6 gauge.

I chose 32 amps for two reasons: One is I realistically don't think I would be drawing more than that at a time in the real world. Two is that it was the amount that let me slip into the 6 gauge wire range for 3% voltage drop and it sounds like that is what people who have upgraded consciously have found to work. And it's still very high. 4 gauge or 2 gauge just seem like overkill. Even 6 gauge is probably ample (right?)

I now don't think the wire size is what got me into trouble over the past week, as I have not been drawing even remotely that much, especially when the fuse blew both times (we have been watching draws on battery monitor). And the 10 gauge wire I have looks to be sized properly for both what I have been drawing and for the main fuse. However, that doesn't cover a short or something like that, so I will keep looking (unless the problem never recurs, in which case I'm going to think it was the unfused cigar lighter).

Unless I read here something I didn't think of about why it would be wrong, I think I will rewire that "helm feed wire" with 6 gauge wire up and back, and increase my fuse block slots with a new block(s), just so I can have a fuse in the block for each thing (and get rid of some inline fuses).

They say that something good comes of even bad things.... well, here I am learning a lot more about electricals on the boat, and I will be making some good upgrades. So that's a plus :thup

Sunbeam

Just to clarify: The Safety Hub is wired between the house battery and the main switch. From the main switch, a wire goes to a positive bus, and from there is where the "helm feed wire" runs forward. That wire is the 10 gauge one (now). Everything "behind" that is #6.

 

[AstoriaDave]

Rewiring with 6 ga and replacing inline fuses with fuse block is a very good idea. Much easier to chase a dead fuse if they are all in one place.

Looking ahead, you may want to run a separately fused 6 or 10 from that positive buss for the heavy current draw items, radar etc., to keep the voltage drop down below 3%. Your total run (both legs) is more than I expected.

If you are using split loom to contain the wires, might pay to put in a size which has room for more wires than you currently have.

 

[Sunbeam]

Rewiring with 6 ga and replacing inline fuses with fuse block is a very good idea. Much easier to chase a dead fuse if they are all in one place.

I think that's on the docket now, thanks to this thread :thup

Looking ahead, you may want to run a separately fused 6 or 10 from that positive buss for the heavy current draw items, radar etc., to keep the voltage drop down below 3%. Your total run (both legs) is more than I expected.

On the total run... maybe I missed something? I don't have my tape measure (victim of the boat-lightening purge), but was just figuring, okay, main cabin is about 6' long, cockpit to splashwell is about 4' long, around corner to helm on forward end is 1-2' long, and "fudge factor" to get into lazarette to postive bus is another 1'. So that made 13' or so, which I upped to 14'. Then doubling that is 28'. Does that sound off or calculated wrong?

I also want to understand about maybe adding the separate wire. I was thinking just size one wire to all loads (minus something for the fact that there is no way I can run them ALL at once), and then run a new one (this seemed to come up to 6 gauge for me). Is there an advantage to running two (i.e. four legs, for up and back for two)? Smaller and lighter? Or?

If you are using split loom to contain the wires, might pay to put in a size which has room for more wires than you currently have.

Good point. Right now "that" wire is just in the big bundle that C-Dory put in along with everything else. But it may pay to separate that into smaller/more bundles. One thing I noticed is that the depth sounder transducer said to run the cable away from power wires, yet it's bundled right in with them (although when I removed it and held it away, it did not work any differently that I could notice).

Sunbeam

 

[AstoriaDave]

Sunbeam,

No, your estimate of the runs seems OK. I had been guessing shorter, not knowing your layout. No issue there.

My main concern is that you may need to run a lot of amps in a worst case emergency or similar. Suppose rough conditions, heavy rain, occasional spotlight use, obscured visibility or darkness. I figured you might be using all of these, not continually, but at some point all might be on: instruments, radar, wipers, spotlight, VHF TX, bilge pumps, nav lights, and horn. That came to 26.1 Amps. No need for the washdown, interior lights or the fan, most likely. But what about those 12V outlets? Would you need one of those to run a navigation app on a laptop? If so, then I think you will be over the 32.1 Amps that slid in under the 3% voltage drop requirement for 6 ga wire to serve your needs.

It might be that the 12 V outlets will have uses you can not imagine yet. If you run a 10 ga circuit dedicated to those, separately fused, then the 18 Amps they might draw does not burden the main circuit to the helm.

Sounds like you are in a good position to work through this and sort out the best wiring and fusing choices for your use now, so you won't have to come back and run another wire later.

 

[thataway]

The 14 foot each way/28 foot is a good estimate; I use 30 to 32 feet because of the twists and turns along the way. Agree with Dave about there may need to be higher current draw, with less voltage drop in the future.

ABYC requires fusing within 7" of the battery. I choose a 60 amp breaker for the main bus feed, with wire sized to handle the 60 amps. None of our C Dory loads are critical to the 3% range--but 5 to 6% is more realistic-number-and that is why I go doubling the wire capacity from the factory wiring.

The person who Sunbeam had help wire her boat, used a 100 Safety hub (which can really handle a total of 7 circuits) for just a single expensive and hard to obtain, 30 amp AMI fuse. . If this is the case, a single circuit breaker would do the same, at less price and then you would not be stuck trying to find the AMI fuse on Lake Powell. As Sunbeam found, the loss of this fuse disabled most of the boat's electric functions, except the outboard motor.

The moral here seems to be understand what you have, and why you have it, in the circuit breaker/fuse protection on the boat.

 

[AK Angler]

Sunbeam - It sounds like you've got a pretty good handle on your electrical situations at this point. That's good to hear.

In regard to upgrading your existing 10ga house feed, AstoriaDave has a good suggestion. There are two basic scenarios to consider.

Scenario #1) Remove 10ga wire and replace with larger capacity wire (in this case, 6ga wire). Also, remove existing fuse block, and replace with larger capacity unit to ensure all new and existing circuits are fused. In this case, you may be banging up against the carrying capacity of the wire in certain (although infrequent) circumstances.

Scenario #2) Leave existing 10ga wire and fuse block in place to run critical systems (maximum 3% voltage drop), and add another wire from a MIDI fuse at the SafetyHub to a new fuse block at the helm for the remaining systems.


After running the numbers on Scenario #2, you may find that with some systems running off of the existing 10ga circuit, you might be able to save a couple of bucks by dropping to 8- or even 10ga wire for the new 10% voltage drop systems circuit. Or (and this is what I would do), you could decide to run the 6ga wire in addition to the existing 10ga for no additional cost over Scenario #1.

In the latter case, you will have moved away from the minimums you calculated to get to the 6ga wire in the first place, and your electrical system will have a bit of extra headroom - it will essentially be "future-proofed". And, this would still leave one MIDI fuse available in the SafetyHub to protect a heavy draw circuit added later - like a future windlass!


So, options:
0) do nothing (must always be considered)[cheapest option - least capacity - most risk for problems]
1) replace 10ga wire with 6ga wire to meet minimum capacity from voltage drop calculations, and replace fuse block with bigger unit [more expensive than 2a, but similar capacity]
2a) as a cost saving measure, install additional 'calculated minimum' house trunk circuit (including additional fuse block), and keep existing 10ga circuit to seperate electronics from other systems [less expensive than 1 with similar capacity; less expensive and less capacity than 2b]
2b) install additional 6ga house trunk circuit and new fuse block, and keep the 10ga wire and fuse block in place for a dedicated critical systems circuit [same cost as 1, more expensive than 2a, but greater capacity than both - overall least risk option]

 

[AK Angler]

The person who Sunbeam had help wire her boat, used a 100 Safety hub (which can really handle a total of 7 circuits) for just a single expensive and hard to obtain, 30 amp AMI fuse. . If this is the case, a single circuit breaker would do the same, at less price and then you would not be stuck trying to find the AMI fuse on Lake Powell.

It's my understanding that there are other circuits wired directly to Sunbeam's SafetyHub 100 in addition to the main house circuit. So, using only a single breaker at the battery would have meant running those other circuits from the helm, adding additional load to the main 10ga house circuit, and unnecessary complexity to the system.

And, I agree: 'The moral here seems to be understand what you have, and why you have it, in the circuit breaker/fuse protection on the boat.'

 

[thataway]

You have the relay trim tabs at 20 amps, and the auto pilot at 15 amps--just there you are over 30 amps. Are these going to draw 35 amps at the same time?You are close to the limit with 30 amps.

Not so. Those circuits are FUSED for 15 and 20 amps. They should never draw anywhere near that much unless there's a problem with those components, which would then blow those fuses before they blow the larger main fuse.

Generally fuses are 25% over the rated draw of the appliance. Some are more for low current draw items. In the above case I put a question? I choose examples with motors. Places where I have seen motors draw excessively;
Lenco trim tabs when the motor meets resistance on the spiral screw. Auto pilot motors as against heavy resistance in rough seas. (Also Macerator pumps and wash down pumps, where an impeller is stuck--that is why there is a slot in the shaft to turn the motor to free the impeller).

Another area I have noted fuse problems in many boats is radios--radio rated a 5 amps--fuse for 5 amps is common. First transmit-blows the fuses, so If I am going on a new boat, I carry a bunch of fuses.

 

[AK Angler]

That's a great clarification Bob, and I agree completely. But, I would add one caveat...

Regardless of the rated power draw of the attached systems, fuses should always be properly sized to protect the wire - and never, never above that. You can always use a smaller fuse if the system draw is lower. But if the calculated system draw exceeds the proper fuse size for the wire, the carrying capacity of the wire in the circuit (either size or number of wires) should be increased before increasing fuse size.

Big wire with small fuses = good.
Small wire with big fuses = bad.


EDIT:
We're really discussing two issues here.

1) Wire size should be determined based on expected load and wire length, so as not to exceed recommended voltage drop limits.

2) Fuse size should be determined based on either wire size or load - using the smaller of the two to choose the proper fuse.

Typically, wire size will determine the maximum fuse size, and load will determine the minimum fuse size.

 

[Sunbeam]

Just got back online - another great bunch of replies. I'll address a couple of things (as far as I understand them)

Thataway: I completely agree on the "understand what you have and why." The electrical system is my least understood one, and although I think the new systems I (and the tech) put in are probably good, it has bothered me not to understand them completely. And then too there are the original parts that I have not gone through yet, none of which strike me as overly robust or elegantly simple.

I'm taking this problem as a "kickstart" to my understanding things better and making improvements (myself). Up until now I had a certain pressure from spending a long time working on a lot of projects and not having used the boat yet. Now that I've had the good fortune to spend a month on Powell with a good friend, I'm a bit more relaxed about another (hopefully smaller!) round, including some new-to-me things (electrical). Also, it's nice to have had some experience aboard to help shape my thoughts on how I might use things (of course more time is necessary )

On the Safety Hub: I agree that there may be other as-good or even better ways, but it does have other uses as it stands now than just the one main fuse. There are my two bilge pumps wired into the top "always live" slots, and there was the Wallas in one of those too (before I removed it from the boat; but I may get a Wallas furnace and so it would go there I believe). I'm sure there are other ways to handle the bilge pump loads, (like maybe another bus or something). Not sure I would get it again, but I'll probably keep it for now (I think?) (and of course carry more fuses - I had only the one in there and one spare).

AK Angler: I appreciate your organized scenarios in options for improving things. I don't have most of those things even on the boat yet (radar, a second 12 volt outlet, washdown pump, electric wipers, etc.) but I do want to plan for them. And worst-case scenarios are good to plan for. I'll have to think over how to do it within the options. I believe I want to replace the 10 gauge wire (even if I do put in two wires) just because it is original, probably not marine/tinned, and I'd like to lay eyes on it (as I replace it!)

Astoria Dave: Appreciate your input and thoughts on "future proofing."

Today's update on the mystery problem:

This morning found us with the new 12-volt outlet in place with its 10-amp fuse, and the "main fuse" being a 20-amp blade fuse on the Safety Hub. I had taped over the trim tab switches so I would not use them. We started out by backing into the beach to change props (I wanted to do a WOT test with my original prop), then headed out into Padre Bay to test it. I had just the VHF/Depth/Chartplotter on - nothing else. About two minutes showed the prop to be woefully inadequate (4800 rpm at WOT) (more details in the other thread I started on props), so since we had 25 miles to go (and a bunch of fuel to burn up besides), I headed right back into the beach to change back to my "Powell prop." After shutting down the engine I turned off the depth sounder, then we did the prop switch, and then pushed off, I lowered the engine, started it, looked back to be sure of indicator water stream, and looked forward to see.... no electronics. Darn! Since I was looking back I'm not sure when they went off, other than that they were on after I shut the engine down and tilted it up when I backed into the beach.

So:

- Nothing was even in the (new) cigar lighter outlet
- Just the three "instruments" were on.
- I did tilt the engine back down and start it (not sure if that affects the main fuse, since it still runs without the main fuse).

Granted, we were on only a 20-amp fuse (jury rig), so maybe it's a completely different issue and not really a "clue." I never expected a 20-amp main fuse to be adequate (but then, it IS adequate for a chartplotter, depth sounder, and VHF (no transmitting done). So I'm back to some sort of short or wiring issue (vs. the cigar socket).

Of course, being "pro's" now, we made short work of robbing the 15-amp fuse from the autopilot and putting that in our slot, and away we went, back to Wahweap. No more issues with electricals. Ahhh.

By the time we got our tow rig and trailer back (had to shuttle to storage and back) it was after 4 p.m. Taking one look at how much work it will be to sort things out (i.e. change from living on boat to van), and also needing to burn off some fuel yet, it was an easy decision to putter back to a nearby anchorage for one more night afloat (yay!) Tomorrow morning we'll take out And then we'll be delving preliminarily into the electrical while still here (mostly looking over wiring for shorts/chafing/other issues), plus cleaning/sprucing/winterizing. Later will come upgrading some of the electrical system -- before the next boat trip (plus laying in a stock of fuses!)

Sunbeam

 

[AK Angler]

While it's certainly disappointing that the new 12V outlet didn't solve the problem, at least you can now rule it out with a pretty high level of confidence. So, of course, the next step is it to check out the main house feed.

Hopefully you won't run out of 'spare' fuses before you get this ironed out.

 

[forrest]

Sunbeam,
Is it possible that you have a parallel connection downstream from your "safety hub" that allows part of the current for your trim relays to pass through the fuse that you are having trouble with? If you have a parallel circuit, the current will be divided over both branches according to their resistance. If the circuit that normally carries the current for your trim relays is partially corroded, the current to run them may be diverted through other parallel paths. Backfeeds can be tough to find and can be a source of intermittent problems. If you have two bilge pumps on one common manual switch, that would be a backfeed. Look for a tie between the two batteries on the load side of your safety hub. You could be getting a backfeed through the hub in the reverse direction while starting the motor if one battery is stronger than the other.

 

[colbysmith]

My best guess says a short somewhere in that main wire going from the fuse that keeps blowing. Perhaps the sheathing chafed off at a screw somewhere, etc.

 

[AstoriaDave]

Sunbeam,

If I understand Forrest correctly, he is suggesting a bad ground on a high current load may be the culprit. A look see, with the aid of a squirt of Corrosion Block and a loosening and retightening of suspect ground terminals may ferret this out without any highfalutin' meter work or other brain cramps. Any ground connections which show lots of corrosion should be replaced ... here is hoping the wiring is marine grade.

 

[anchorout]

Sunbeam:
I know this is all confusing, but it is very hard to troubleshoot over the net, without being onsite to physically see how things are wired. These boats were probably originally wired the same (I have schematics in my owner's manual). But most have been modified to carry more current to feed more goodies. The boat I recently bought had a separate fuse panel under the sink. I spent 3 days straightening out the wiring.

Personally, once I understood where and how the safety panel was used, I have ordered one for my boat. It beats having multiple runs with inline fuses, all piled onto a battery terminal.

On my boat, the engine circuits, that is the tilt/trim, dash engine instruments, starter solenoid, etc are insulated from all other circuits on the boat. In other words, nothing I do with the engine should cause current to run down the wire to the main fuse panel. In your case, through the 30amp fuse. So, on your last episode, either something is wired so as to cross talk with the engine circuits, doubtful, or we are still chasing the elusive short circuit.

Whatever the fix turns out to be, I'd give you a free ride to fish the rigs in the Gulf to know what you finally find. Again, good luck.

 

[Sunbeam]

While it's certainly disappointing that the new 12V outlet didn't solve the problem, at least you can now rule it out with a pretty high level of confidence.

There is that!

Hopefully you won't run out of 'spare' fuses before you get this ironed out.

Ha ha, see next post.... "Okay, what should we pull next..."

My best guess says a short somewhere in that main wire going from the fuse that keeps blowing. Perhaps the sheathing chafed off at a screw somewhere, etc.

A preliminary check last night didn't show anything, but there were a couple of spots I could not see. Tomorrow I will be going over every inch of that wire with a fine-toothed comb. Sure would be nice to find some glaring flaw.

If I understand Forrest correctly, he is suggesting a bad ground on a high current load may be the culprit.

Another thing to check out. Although that said, I don't think we had any high current loads during the last three episodes. But we're going to just look at everything closely tomorrow. Will be easier now that we're not worried about taking apart our boat "at sea," and with lockers emptied.

Sunbeam:
I know this is all confusing,

You can say that again!

... but it is very hard to troubleshoot over the net, without being onsite to physically see how things are wired.

I do realize that, and it makes me appreciate everyone's help all the more. I'm sure if you (or others) were here you'd have it figured out in short (ha) order

These boats were probably originally wired the same (I have schematics in my owner's manual). But most have been modified to carry more current to feed more goodies. The boat I recently bought had a separate fuse panel under the sink. I spent 3 days straightening out the wiring.

And to add to that, I think that many of the dealers did some (or most?) of the wiring, so there was no "standard." That said, my boat at least hasn't been "piled onto" by a bunch of owners (had 52 hours when when I bought it). Basically it looks like it was oufitted nicely but minimally when new and then never changed (until I came along and started a refit, but electrically, I have only gotten as far as the battery/lazarette area, plus adding the trim tabs and a battery monitor - I have not done much behind the helm yet).

Personally, once I understood where and how the safety panel was used, I have ordered one for my boat. It beats having multiple runs with inline fuses, all piled onto a battery terminal.

Neat - I'm glad you were able to get a helpful idea from the thread.

On my boat, the engine circuits, that is the tilt/trim, dash engine instruments, starter solenoid, etc are insulated from all other circuits on the boat. In other words, nothing I do with the engine should cause current to run down the wire to the main fuse panel.

I see. I think mine is that way too (e.g. a blown main fuse does not affect engine running or engine gauges - they still work fine), except that since I have an ACR (automatic charging relay)... I guess that means that when the engine is running and the ACR is "on," then current can be "sucked" into the house system from the engine charging system. Is that still considered a "connection" or would you say my engine system is "insulated" like yours?

Whatever the fix turns out to be, I'd give you a free ride to fish the rigs in the Gulf to know what you finally find.

Well shoot, now it's starting to sound like the whole thing is worth it Thank you for the invite - that would be really cool -- but of course I will report back in any case. Threads without follow up drive me nuts!

Okay, summary -- including #4, #5 and #6 (yep) in next post.