Not to discount what you guys have said it does make sense! What I was told by 2 people at the river, that recenty had same problem-- the shop do not pull the built-in tanks out of boats to completey empty them, They have a guy come by and pump gas out. then put new gas in and test run. I can only assume some gas is left in tank. This gas can not be helpful to new gas, but I am hopeful it will not affect it bad enought to prevent burn off. AS it does burn already. ( just not well)
Again I am open to all suggestions and not knocking ANY!!