I am on guard duty here looking for things that might burn my boat down.....
One of the troubles with owning a boat is that a little knowledge can become a dangerous thing. Most boat skills, including maintenance, navigation, boat handling, and sail trim, are very hard won. It can take years to even learn to talk the language of boating. Then, there are some arcane sciences that can even be more daunting - one of these is DC system installation and maintenance.
I think the thing about boating today is that so many people want the boat to be a car - you just turn the key and go - these are all the folks you hearing calling for "Vessel Assist" on bright sunny summer mornings when their batteries run dry, their alternators fail, and they are generally high and dry with no wind.
I have developed some modest understanding about DC (direct current) systems. I rebuilt one system on my old Hunter 34 that involved a new, high output alternator, new batteries, battery control switches, etc. Though I did not know it all, I knew more than most - that little bit of knowledge led me to mistakes that could have burned the boat down.
Our Malo 39 came standard with a Hitachi 80 amp N-type alternator - with an internal regulator. This alternator will not put out enough juice to keep a flashlight going - you will run your engine for hours and hours to produce 80 amps. I think the highest output rating I ever saw on it was about 45 amps and this was with fully discharged batteries. I knew I needed a high output alternator with smart external regulation - that is regulation that measures the voltage at the battery and adjusts the flow of electricity out of the alternator - it typically follows a bulk, absorption, float model that the batteries need to survive.
There were a lot of manufactures in this area. I chose Ample Power because of their reputation, their close location to my boat, and the high quality of the technical advice they provided. I installed the 4023 alternator, rated at about 125 amp output, their V3 regulator - and their "Eliminator" to connect the starting and house banks. I won't bore you with the arcane nature of this stuff - lets just say it was a complicated job involving a lot of wiring - going from the alternator to the regulator to the batteries - which were mounted about 18 feet away.
I really screwed up sizing the wiring for the alternator output - which is what this post is about. I was so happy that Malo had installed a very nice cable for me to use to move the power from the alternator to the battery bank - of course I could reuse their cable! I read the instructions, read Nigel Calder- the installation guide from Ample had the wire sizing chart right out front. But I did not see it, and did not realize that I was producing about 3 times the power that cable was sized for!
The little wire - I estimate about a size 6 or 8 - was installed by Malo. The bigger wire is the right size for the new alternator - a 0 gauge - there is a significant difference between them.
How did I find out about this problem - my system had been running perfectly, or so I thought, though its output had never been what I expected. I started watching all of these cables very closely after installing the wind generator, and I found that the old output cable was heating up - so hot in fact that it was burning the insulation. It had held together OK for about 2 1/2 years - or maybe I had never grabbed it when it was in bulk charging mode - who knows - I screwed up.
When I explained this to my poor suffering wife, she pointed out to me she would never buy me another boat if I burned this one down.
Malo installed great tubes for moving wires back and forth along the boat - unfortunately, these were all filled, and/or too difficult to access. I had to install wire bundles, which are mounted outside the tube. The AC wires are separated from the DC wires, inside their separate black plastic insulation tubes. In hindsight, I could have asked for a tube for my own use - if only I had known.
I was able to insert the 0 gauge wire into one of the tubes under the settee - what a lifesaver - thanks Malo for leaving me an opening - they used one side of the tube, leaving me enough space in the other to get the wire through.
The wire came out from the tube, and snaked around the water pump.
That's the wire going into the alternator. This wire is heavy, and is secured above the alternator on the bullkhead with an insulated clamp to provide support.
The wire from the alternator goes directly into 
the battery bank. I decided to bypass the switch bank for this - since there is no need of a fuse between the bank and the alternator. The output wire is the big boy on the far left.
So - just where am I going with this post? When I bought the boat - I was afraid to touch anything Malo did - just assuming it was right. Now I am changing things, and have to go in and resize wires to match the new systems. I need to think a little more clearly about what I am trying to do. If I really screw up - I may not get another chance....