Engine

Hey guys, new here. I own a 22' Key West w/ a Honda BF130 4-stroke. I'm the 3rd owner, have no manuals, etc. and am stumped. This is what happens: at idle I can trim/tilt all day long. At moderate or WOT and engage the tilt/trim switch on the throttle or the switch on the engine, the engine stalls out/cuts out. If you keep the switch depressed it will kill the engine. If you let go, the engine picks right back up. Obviously I have a short somewhere, but where to start? Tried to isolate the switch on the cowling by disconnecting, but cant see how this is done. The switch/connector seems to be a single molded piece. BTW, if it matters, the battery (only one for now) IS on its way out, gettin weak. Thanks in advance for the help!