SDA: Sdowney, some good comments and an opportunity to further expand on issues with solder, my responses follow:
Never seen a wire snap off yet becuase it was soldered.
SDA: I have, on several occasions, especially in high current applications. It is prohibited by ABYC for exactly this reason, it can and does happen.
If any solder flows down a wire hardening it, the unsoldered wire is the relief for movement.
SDA: Provided it is free to move, if it's bundled or secured with a P clip it is not free to absorb movement where there is no solder.
And few wires I soldered ever wicked solder.
SDA: Marine grade Type III wire, which is finely stranded, and preferred where there is any chance of movement (essentially anywhere aboard a boat) wicks solder readily. Type III #12 wire for instance, has 65 strands, Type II has 19 and is IMO too coarse for reliable marine use.
I have serviced a lot of electrical equipment and every wire is soldered to a board, including inside generators and never seen it happen. If you told the designers of the equiptment you could not solder wires they would laugh you right out of the building.
SDA: "Electrical Equipment" and boat system wiring are very different. ABYC does not prohibit the use of solder within enclosures, radios, inverters, radars etc. Those are mass-produced production components. What they prohibit is a boat owner, builder or marine electrician from making custom soldered joints at electrical panels, junctions, and terminals.
If a poor screw connection is causing wire to get that hot to melt solder and the wire falls out of a terminal, that would be a good thing,
SDA: Not necessarily, if the wire is energized and makes contact with a grounded surface, or worse make a connection between the AC and DC system, that would be far worse.
breaking the connection, never seen it happen. I have seen electrical plugs which are not soldered overheat and melt and they stay together, is a bad thing.
I have seem lots of old crimps and there are usually corroded wires where they meet terminals., and the corrosion can cause the strands to break, seen the insulation pull back from a crimp exposing wires which then have no support == broken strands. I prefer to remove the plastic off a crimp and use heat shrink. Never seen that fail or corrode.
SDA: You can buy heat shrink terminals, not sure why you would remove existing insulation from a solderless terminal, seem tedious. Or, if you are looking to augment strain relief either use double crimp terminals, which include insulation strain relief, or add heat shrink over the existing terminal's insulation.
I have worked on cars a lot, used to be a mechanoc, facts are the plugs, sockets where wires join to wires are always the worst failure point. The terminals loosen up due to heat from current flow over many years, high resistance develops, then the whole plug starts melting and the wires and terminal corrode and it fails.
SDA: Those are less common on boats, at least the ones that are not mass produced. You see them for engine harnesses, most every other connection is essentially custom made, using solderless terminals, and they are extremely reliable of done correctly (virtually every military and civilian aircraft uses these, they do not use solder).
And some of those failures are very hard to find, everything may look ok, but you get intermittant connections. Had that on an Isuzu Trooper, one of the wires for the TPS in the plug for the engine computer, failed due to it must have gotten too warm or just lousy design , spring contacts fatigued. The fix that worked was soldering a long jumper wire around the 3 wires at the connector, had to open the computer and trace the circuit board for the TPS and it never was a problem again. High current plugs are especially bad, devices like blower motors....
I just installed a new radio, OEM power wires were too short by about 3 feet. I took some 14 gauge wire, and twisted the ends together inline and soldered them together, then heat shrinked it, and it will never be a problem. Any needed flex will be provided by several feet of wire on each side of a 1/2 inch long solder connection point. Now if I took pliers and grabbed the wires at the soldered joint and started bending them back and forth the connection would break eventually. Who is going to do that. Same breaking apart would happen with a crimped but.
SDA: While this may work, the reliability of such a connection depends a great deal on the soldering skills of the Installer, and if you've ever tried to solder where there was even a gentle breeze, on a fly bridge for instance, you know it's very difficult indeed. You could have made the same connection far more easily, safely and reliably using a high quality, heat shrink if you like, solderless butt connector. No boat builder or marine electrician I know uses solder.
However incompetant solderers should not solder anything. Its a learned skill you have to get through years of technical training to achieve competance, yeah sure it is,
SDA: I agree, an unskilled solderer can get into a lot of trouble very quickly.
However, "years of training"? I believe that's a bit of an exaggeration. But if that were true it makes a very good case against soldering.
(in Kaohsiung, Taiwan)