I have a 1998 searay FX16 with a 175HP merc.at 1200 rpm which used to be a smooth idle it is very erratic like 2-3 hundred rpm jumps but not constant it does not stall but very annoying, I have changed plugs, checked for spark, cleaned out gas, changed filter etc.all were good and no change. it has full power and runs great at 5500 rpm. At 1500 rpm it is not erratic but seems a bit ruff. There is more smoke on cold start ups than I noticed before.Any suggestions appreciated
