Dual fuel tank

[moose68]

I have an 89 mercruiser 260 in my 21' daytona. It will run just fine on starboard fuel tank, but when on the port tank it will idle and run at slow speeds but as soon as I throttle up it will either die or just sputter after it barely gets on plane. It will start right back up on the same tankand repeat the same thing. Could this be a problem with the tank vents possible plugged, I have torn the panels off and can't find any vents. Do you have to have a vent? Anybody have an opinion?

 

[rbezdon]

Re: Dual fuel tank

All tanks have vents. It is always necessary to allow air to enter the tank where you remove the fuel from during running. Yes, your problem is likely in the vent, pickup line in the tank, antisiphon valve on the tank or in the lines from the change over valve.

 

[moose68]

Re: Dual fuel tank

I can't seem to find the vents. They are side mount tanks, I've checked the area around the sending unit and fill hose. It has the flush screw in cap. Could the vent be part of one of those items. What is the antisyphon valve, not familiar with that term.

 

[rbezdon]

Re: Dual fuel tank

Antisiphon valve is a 90 degree fitting (usually) right on the tank where the hose from the fuel pump (or seperator or what ever is going to the engine fuel delivery system) attaches to the tank. Inside of it is a ball check valve which causes there to need to be some "suction" from the tank to get the gas out. This is a US Coastguard requirement for all premanent tanks so if the boat "flips", the siphoning action can not cause the fuel to all drain out due to siphoning action. Since this is a law, all boats made with inboard permanent tanks have them just like vents. The laws of physics require a vent so you have one somewhere. I dont know if it is common on inboard tanks but I know some outboards, lawn mowers, snowblowers can have the vent in the gas cap. <br /><br />By the way, the puck up tube is the tube that extends down into the tank from the antisiphon valve to the tank bottom to allow fuel to be picked up. There is a screen on the end of this tube which it is common to have get clogged with tank crud. There are several posts on this and the dramatic improvements when this is fixed.