One fuel line to two engines

Ifishmuskie2

Seaman
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Oct 5, 2025
Messages
57
I searched for the answer but i can’t find it.
I have one fuel tank and one line coming out. I have a main and a kicker. I was thinking of installing a selector switch but then I have to switch it all the time. What about installing a filter with two outlets? Would that stop one engine from pulling fuel from the other? I don’t really need a water separator.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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What about installing a filter with two outlets? Would that stop one engine from pulling fuel from the other?
nothing

its been discussed before. you actually end up drawing air in from the carb in the kicker and you basically run out of fuel on your main.

if you have a below deck fuel tank, there most likely is another location you can plumb in a pickup tube.
 

Jeff J

Chief Petty Officer
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Jun 23, 2021
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460
I think a primer bulb or some other check valve on each line coming from the filter would take care of sucking air through the other engine.
 
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Jeff J

Chief Petty Officer
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Jun 23, 2021
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A 3-way valve on the filter outlet would take care of it too. Maybe that is what was meant by “selector switch”.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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I think a primer bulb or some other check valve on each line coming from the filter would take care of sucking air through the other engine.
you would think so, however it doesnt. also, a primer bulb on I/O's is not allowed.

the OP has two outboards. so it could work. the cheesy flap check in the primer bulbs work for a while to prevent issues, however can fail, especially if the main motor is an I/O

and a 3-way marine fuel selector valve is kind of pricey
 

Jeff J

Chief Petty Officer
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Jun 23, 2021
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I always wondered why the I/Os in the fleet didn’t have a primer bulb. They sure come in helpful when a boat gets run out of fuel.

An on/off valve on each line maybe? But that brings us back to switching.
 

Ifishmuskie2

Seaman
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Oct 5, 2025
Messages
57
I guess the selector switch/valve. Is the best answer.
I fish with a friend and he’s always telling me to go back and turn the switch so I guess I’ll get the co pilot to switch it when I’m driving lol.
 

Jeff J

Chief Petty Officer
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Jun 23, 2021
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DANG! Even fuel valves for aircraft are not that high. Here I thought there is nothing more expensive than aviation.
 

airshot

Admiral
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Jul 22, 2008
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6,245
Most small out boards have a quick connect right at the motor, so why not just unplug the fuel line when not using the kicker ? Years back I added a primer bulb to the fuel line on my I/O as it had a 10' long run to the tank. When I had my safety unspection, the inspectors saw it and said it was a good idea....never said a word about being illegal....
 

Ifishmuskie2

Seaman
Joined
Oct 5, 2025
Messages
57
I could be switching from main to kicker ten times in a trip as I move to different spots.
That’s why I’m looking for the easiest way.
 

tphoyt

Lieutenant Commander
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Jun 10, 2010
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1,989
If you went with your plan on using both outlets on the filter you could add an inline shut off to the kicker. Of course you would still need to turn that on and off each time but it’s quick and easy. If you have to add said filter may as well go with a water separator as every boat can benefit from that.
Just a thought.
 
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