mercury fuel line size

mercury 150 serial number od198941 just a quick question I have 3/8 fuel hose ran from my motor to my bulb then all the way to my water separator .I was told the other day to run 5/16 from my motor to my bulb then 3/8 from my bulb to my water separator . question is would it make the motor run a little rich running a 3/8 hose all the way like I have now thanks for any info.

Nope 3/8 hose all the way to the motor..

Sorry- you need to read the information here:

FUEL LINES AND PERFORMANCE PROBLEMS