I had the same problem once, but not on a bayliner.... mine was a carbureted engine and it was found that the floats were set too high, so when the engine was shut down the heat of the engine would rise into the carb and expand the fuel enough that a few drops of gas would escape thru the overflow into the throat of the carb, then vaporize causing the smell.... the floats were adjusted accordingly and the problem went away.
if your engine is fuel injected, then its highly possible that you have either a bad injector, or a very slight fuel leak somewhere in the system... when the engine is running, it ingests the fumes/air from the space so you dont notice it, but when you shut it engine off, the fuel vaporizes and fills the spaces. when the engine is cold or after the fuel pressure has fallen off in the lines, it doensnt leak or vaporize.
a bad injector can drip fuel onto the hot piston after the engine is shut off while the pressure is still built up in the fuel line... then if the intake valve is open it will vaporize and expand back thru the air filter into the engine space....
a small leak may not be much and hard to find, but a very small amount of gas will make a lot of fumes when it gets warm, and enough gas fumes in the engine compartment will eventually creep into the living space of the boat.
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