CONTINUOUSWAVE

My [unidentified Boston Whaler boat is rigged with a] Mercury 40 HP EFI outboard that has a 1/4-inch ID fuel hose under the [engine cowling]. That hose mates with a 1/4-inch to 3/8-inch adapter in the [stern] that is on a hose that runs to the [fuel] tank. I do not understand why a 3/8-inch or 5/16-...