ok im a jetski mechanic for a rental company thought i seen it all but got a new one i aint seen before we have a 08 vx sport idles great but when you give it throttle it will rev to 5000 and start slowing down spitting and skipping and when you let off it has a massive back fire we have tried new computer injectors plugs coils we tried adding some carb cleaner to see if it would help it rev higher just bogs it out any ideas guys?
Here's a few things to check. Bad crank position sensor, bad tps, Water in the fuel system, dirty filter or pick up in the tank, timing is off, engine is seizing.
Have you done a compression check ? Need to use a actual water remover, or drain the fuel system completely. What did the plugs look like ?
My gut is telling me crank sensor or a problem with that specific wire harness.