300 x HELP

[steve berry]

i have a 2002 300x it will run down the lake but it stalled at 2800 rpm but started again then stalled 5 minutes later at 5000 rpm it is newly rigged new harness found no clamps on oil lines fixed it res bottle on motor now filling lots of gas it is like someone just turned off the key no horn sounding and no codes when i scan it so what is the problem i also put in a new tack trim gauge water temp its not overheating all new gauges are mercury and a couple are suzuki amperage and fuel any help i can get would be great thanks steve berry ps the gauge harness is also new thanks again steve

[johnmiffco]

did it stall when hit bumpy water/wave? as have seen the tether kill switch do that quite few times through the yrs ,,,,did u put on a new 1 with the harness or reuse old 1 that was in boat,,,,can unplug it and ck also a loose battery wire or connection will do it also,,,the ecu drops below 11-2 volts,,,shuts off,,,

[25two.stroke]

If the 300x still has smartcraft in the ecm then look and see if you can read the number of estop occurrences. Not sure what year they started logging that but most of the time that will show a faulty kill switch cause there will be lots of times the kill was activated and de activated. Like he said above loose/bad battery cables will do that. Check both ends of the battery cables and make sure the ground cable on the engine is hooked to the block not to the starter cap like they do on 2.5L motors.
First thing I do when I have something like that is I check the fuel pressure running. Then I check the fuel pressure with the motor running but pinch the vacuum reference from the regulator off. If the motor runs the same and the fuel pressure only changes 1-3 psi then thats all good. Next step is put a 17 or 19p aluminum prop on it and back it down the ramp and run it under a load all the way up to 6000 watching the fuel pressure. If you have a piece of junk floating around in the vst or a fuel pump just starting to fail it will intermittently die. I just fixed a 300x with that same issue. Fuel pump worked fine at idle and up to about 3000 rpm...after that it just started fluttering from 20 to 40psi and then eventually if you kept running it then it would bog and die. Bad high pressure pump just starting to fail. Dangerous cause it could burn a motor up.
If fuel checks out then I would hook a new boat wiring harness to it and just lay it in the boat and go for a drive. Don't hook up any of the gauges or other nonsense. Just a key and a wiring harness. See what it does.

[Wild Bill]

Make sure all the pins on the cannon plug on the motor are clean and are connecting. I had an issue like that, pulled the plug expanded the pins and dielectric greased them so far no more problems

[steve berry]

thanks to all you wonderful scream and fly members for your help thanks thanks THANKS AGAIN STEVE BERRY