Ok. I am at my wits end with this thing. I have changed the trigger, power packs, cleaned the carbs, new lower unit, new prop shaft, new prop and new shift cylinder. Here is my issue. I start her up and she idles fine. I can rev it up in idle and it is fine I put it into gear and it starts moving. I give it a minute or so and start to give it more throttle and it will back fire or kick however you want to look at it. What in the world is going on here? Can anyone help?