I have a 1996 johnson 130 looper and on a recent trip I was returning to the dock at wot 5500rpm and all at once i droped down to 4500 rpm, engine ran fine, no alarms, but would not run past 4500. Engine would surge from time to time but that was all. When i got home noticed one of the spark plug wires was nearly burned in two so i replace all wires and plug, next trip same thing only run at 4500rpm. Came home replaced fuel filter, flushed lines, install fuel pump repair kit check all hoses and next trip did same thing. Any ideas of what to check next?