The combination of numbers and letters you provided—393778, 140 MX, and 23 D J—refers to a few different components and identifying features of a classic Johnson outboard motor from the mid-1980s.
393778: This is an OEM part number (also written as 0393778) for a V4 lower carburetor assembly...
I had originally planned on adding a 1/4" in-line pressure reducer with a 0.50" to 0.625" orifice but decided to go with a locking needle valve that I may adjust the flow, which in turn adjusts the PSI on the carbs. Fingers crossed. I'm going to try this set up. ;)
saltchuckmatt - It is a standard 115 outboard. Not a VRO.
Chris1956 - Yes, the VST is simple and causing me issues. I did replace the cover gasket and filter, as well as ensuring all the hoses feeding it had a good seal. I agree with the electric fuel pump leading to problems. Unfortunately...
Can this system be successfully done by adding a 4 - 7PSI electric fuel pump, heat protective hose sleeve to fuel lines, and a Wix 33041 fuel filter with restricted bypass returning to tank? If yes, is anyone able to help me identify the purpose of all the hoses attached to the VST? I have no...
