Larry,
Do yourself a favor and have the engine checked out. I had a 115 Yamaha that gave me two very brief periods (i.e. 30 seconds) of rough running. I thought I had a bad tank of gas or fouled plugs. (Yes, the oil injection well was full of oil.)
$6,500 (borrowed dollars) for a new Suzuki and 1/2 of 1997 season-both make me wish I had it checked out...
(PS-My main bearing went. Not exactly preventable without professional help.)