marine vs automotive electrical components
I assume there is heat applied to the bit of solder in the crimp barrel?
Seems reasonable to me, like tinning the connector.
I have dunked wire ends into vaseline before putting on a crimp connector for a long time. I remembered this after I had already posted my comments. dielectric inside a piece of shrink is a good idea.
The fact that selling something as a "Marine" item adds 500% to it's price over "Standard" stuff, be it electrical or otherwise, makes creativity in "marineizing" stuff ones self cost effective. I used 2 ga.welding cable for distributing 12 volt power in my Albin Vega, between batteries, main switch, and distribution panels successfully for years. I tinned connecting ends, heat shrink sealed the insulation cuts, and applied dielectric grease to all the crimp terminals, and ran it all well above the bilge. Worked just fine, and cost many dollars less than fully tinned marine cable. Regular inspections and resistance checking showed up no deterioration in 10 years.
I once had to replace the power cable to a submersible pump in a sump at the bottom of the periscope well in a Sturgeon class submarine. It had been installed with non tinned wire, and the copper strands were corroded into black powder. I would not advise welding cable for this sort of application.