When I worked for Ak Clean Seas on the slope we had balanced and blue printed 502's, I thought this is the only way to go. Then last week in Cordova I was on my buddies airboat w/ a Continental aircraft motor and we fueled it up w/ the infamous Shoreside petroleum Avgas and fired it up only to have it die and we couldn't re-start it. I noticed water coming out of the over flow from the injector pump. Low and behold we noticed the racor filter was full of water so we proceeded to purge 2 gallons of water out of the tank, thankyou Shoreside! What amazed me was after we changed the filter and purged the tank the engine fired right up and ran great. I know for a fact an automotive engine would not have fired until we pulled the plugs and blew the water out of the cylinders. Were we lucky or is this normal for aircraft engines?