2003 200 EFI Mercury usually runs OK heading out to fish. Shut big motor down troll for awhile. When it's time to come back in or move to another location, it starts right up, throttle up and engine dies, start up throttle up and engine dies. Runs fine at idle, but it dies when I try to get up on plain. I had in at Merten Marine in Oshkosh twice. They keep the boat for more than two weeks each time. Payed them over a thousand dollars and it still doesn't work. Anybody have any suggestions?