Fuel tank issues

HangoHango Member Posts: 1
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.

Best Answer

  • Liberty44140Liberty44140 Member Posts: 4,221 ✭✭✭✭✭
    Answer ✓
    One thing to keep in mind is that with all three valves open the fuel will take the path of least resistance. Generally you see this in one tank's gauge dropping a little faster than the other. In your case one is probably so blocked that it is always taking from the other so when you force them to take from their respective tanks, you get a problem.  Agree with LR, I'd inspect (and probably remove) the lines from the engine to the wall as a start. Make sure that valve is clear. 
    07' Cruisers 390 (Previous Rinker's: 06' 342EC & 01' 310FV)


  • LaReaLaRea Member Posts: 7,345 ✭✭✭✭✭
    Welcome to the forum.  I'm guessing you've already inspected the fuel line all the way back to the tank for kinks or damage.  Maybe the valve isn't opening.  Could you disconnect a fuel hose at the engine, and use low-pressure compressed air to blow back into the tank?  
  • Pat310Pat310 Member Posts: 517 ✭✭✭
    Welcome Jim 
    I think you and @LaRea are on the right track. Sounds like a clogged vent or pickup. Try turning off starboard tank, open port tank and crossover and run the starboard engine off port tank and see if it gets the same backfire.  
  • LaReaLaRea Member Posts: 7,345 ✭✭✭✭✭
    I don't think a blocked vent line would do it, but you could try running with the fuel fill cap loose.  
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