I have a 2011 BF50D with 1048 hrs of running time on it. It powers my 17' Sylvan sea Monster fishing boat. It has performed flawlessly up until 3 weeks ago. The motor starts no problem, idles fine and runs perfectly up to 3/4 throttle. As soon as you attempt to accelerate beyond 3/4 throttle, it starts surging (bucking) severely until you throttle back to 3/4 or lower when it returns to normal. I have so far changed a complete new fuel line from the tank to the motor, replaced the low pressure fuel strainer, replaced the high pressure fuel strainer and added a can of Seafoam Marine to the fresh gas in the tank. The spark plugs have 20 hours running time them and all appear to be burning fine. Don't know what else to try and the closet dealer is about 80 miles away. Any thoughts???? Thanks