hello i have a 2hp mariner model 2b 6A1 078449. when i try and start it in water it will not even attemt to fire, but if i take it out of water it either starts and runs for 3-5 seconds or just tries and fire up? i started it and put in water and it cuts out ? i have fresh petrol, clean spark plug what sparks well and cleaned the carb. the sparkplug is getting soaked in petrol when i try to start it.