I was out fishing today boat was running fine til I started to troll I diden;t go to far when I got an Alarm lasted for 40 to50 seconds then stop,I shut down the boat and started it again no problem I thought til I started to go it would only let me go 4 to 5 knots and if I went faster I would hear pop pop pop like it was misfireing??? Anybody I don't have a clue where to begin to look. Thank's for any help 
Art