Fuel tank issues
I have a 2003 Fiesta Vee 290 with twin 4.3 mercruiser motors. The boat has 2 75 gallon fuel tanks. The boat was in dry dock for almost 2 years and was re commissioned mid summer this year.
When I run the boat off both tanks with all 3 ball valves open the boat runs fine. When I run the boat with just the starboard tank open (on) feeding both motors the boat runs fine.
When I run the boat with the port tank feeding the port motor and the starboard tank feeding the starboard motor the port motor backfires and will not pull.I have changed the water separators and drained the port tank and put fresh gas into it. This did not help. I also replaced both fuel caps.
To my thinking I must have either a clogged fuel pick up or the vent line is inop.
Any idea how I would trouble shout this and if need be clean or replace the fuel pick up. Ive never seen a schematic or parts fish foe the fuel tanks.