View Full Version : Fouling plugs

08-19-2009, 08:19 PM
"Hi, i just bought a 95 yamaha 25hp oil inject. a few mts. ago ran great. Now it's starting to foul plugs up, on trolling speed, not both at the same time. Is it the type of oil that causes it. I've tried different types.Tried some yamalube ran it for 7hrs at low idle plugs looked good.Just wondering if it could be the oil or something more serious."

08-20-2009, 08:49 AM
"hopefully your thermostat is operating correctly to allow engine to reach normal operating temperature. if it's not then you may have a rich,start-up mixture all the time, which would fowl the plugs. I run the Pennzoil Marine 100% Synthetic oil(Walmart $27/gallon) in my 90HP Yamaha and it burns very clean with little smoke. also, be sure you have the correct specified spark plugs for your motor, since a plug with a different heat range could cause fowling. if your motor/fuel/oil are all correct you should not be fowling plugs much at all. I bought a spark plug sand blaster at Harbour Freight Tools and it works like a charm to keep plugs like new. the thing costs about $18, pays for itself over and over for all spark plugs. In fact I'm still running my original 1999 spark plugs and they're pretty much like new! Good Luck!"

08-22-2009, 04:59 AM
"Tkx for the reply, the yamalube seems to be working for now. Is there a site some where that shows where parts are located and how to fix it ???."