Just started noticing lately how much gas my outboard has been using lately. Not sure if I have a motor issue, or if I just happen to be paying more attention. I have a 1997 100 hp 2+4 Mariner 2 stroke, on a 16.7 Ranger Fisherman. Last time out I went on Lake Michigan for a 4 hour trip from put in to take out, with the majority of the time trolling, on a nice calm evening. I used 9 gallons of gas, and only had 2 gallons left, which gave me some concern when I found out. On the trip before this one I was on the wolf river, and also used more gas than I thought I should have. Anyone have any input, if this is excessive or would be considered normal. If it sounds excessive, any thoughts on what could be causing it.