Years ago my grandpa told me how he checked the spark plugs in his old 35 horse Sea King each year before running. The first thing to do is take the boat to a lake (clear water prefered), remove the spark plugs, one at a time, and place them in the palm of your hand. Slowly lower the plug into the water, then turn your open hand palm side down, watch the plug carefully. If it sinks it's time to replace the plugs. Try this on your outboard it may save you alot of problems later.