Tenmile gives good advice above. If you receive better without the screw on part of the connector attached, you have a short somewhere. Could be your coax, could be the antenna but I’d bet on the coax connectors.
For sure solder the connector on the end, if not, in short order in a marine environment it will corrode and make a bad connection.
If the coax will unscrew from the antenna, and you have an ohm meter, measure the resistance from the Center pin of the coax to the ground side with the screw connector. It should read zero, if it doesn’t, you have a short in the coax. Cut the connectors off and solder in new ones.