rg 8u is nominally .405 diameter, while rg 8x is .240 diameter. That is, one is almost 1/2", the other just under 1/4" diameter
wrong connector and depending on the chase or conduit you are pulling the coax in, it may be too large for your application.
the connectors are not the correct type for your cable, nor is gold plated brass a needful thing.
Buy only amphenol silver plate/teflon connectors, nothing else is worth installing, especially in a marine environment.
You will need at least a 100watt soldering iron (not a torch) and appropriate tools to make the connections. Small soldering pencil will NOT apply enough heat fast enough to flow solder without damaging the coax or the internal insulation.