Fuel pumps and Aux. fuel tanks

[JRatliff]

I have a Wellcraft 248 Offshore with twin Merc 150's. The main fuel tank has 125 gallons and then the previous owner added a 50 gallon Aux. tank in the bow. The boat runs perfect from the main tank. When I switch to the aux. tank I get air in the fuel lines whenever I am in seas over 2 feet.(Lots of bobbing around with the bow and air gets in the fuel lines). <br />My questions are: <br /><br />Is there a fuel pump that I can use that would work in addition to the engine fuel pump? <br /><br />Can I install a inline fuel pump near the aux. tank up front without having to much or to little fuel pressure driving the eng. fuel pump?<br /><br />I have also thought of just transfering the fuel from the aux. tank to the main tank when the main tank burns down 50 gallons. With this setup I would need to know when the tanks runs dry inorder to not burn up a fuel pump.(I don't have a fuel guage on the aux. tank). Maybe a fuel low pressure switch that would turn a light on or turn off the pump when the pump stops pumping.<br /><br />I am trying to keep it cheap, simple and safe. I don't want to be blown out of the water with a cheap fuel pump or a non "explosive safe" pressure switch.<br /><br />Has anyone been across this problem before? Any ideas on specific 12 volt pumps or pressure switches? <br /><br />Any suggestions would be greatly appreciated.<br />TIA<br />JR

 

[The Marine Doctor]

Re: Fuel pumps and Aux. fuel tanks

Is there a problem when the aux tank is full?<br /><br />The shape of the tank might be a problem. The fuel sloshes around and leaves the pickup open to air. <br /><br />The pick up might not be deep enough into the tank.<br /><br />TMD

 

[JRatliff]

Re: Fuel pumps and Aux. fuel tanks

Hey Doc,<br /><br />You are correct... When the tank is full there is not a problem. And when I am running in smooth water its OK. I am getting air bubbles in the line when running from the front(Aux) tank, only in rough water. It is a square tank. <br />I was thinking about adding a small 12v pump by the front tank that relieves pressure when it is too high and keep the engine fuel line charged at 2-5 psi. Or, I could just add this same pump inline and open the Aux tank valve and at the same time open the main tank valve and any extra fuel that the engine does not need would just reverse flow into the main tank. With this I wouldn't know when the Aux tank would be empty and I wouldn't want to keep burning up 12v fuel pumps. So I was thinking of a low pressure switch to turn on a "Low Fuel Pressure" light or just turn off the pump.

 

[JRatliff]

Re: Fuel pumps and Aux. fuel tanks

Doc, <br />About the Pickups...<br /><br />They are welded in place so I could not take them out to measure... however I did get a clothes hanger and bend a small 90 degree angle in the end. I was able to stick it down the tude and feel the end was about 1/4-3/8 of an inch from the bottom. The pickup tubes are also mounted in the aft portion of the tank.<br /><br />I need some way to keep positive pressure to the engine or just transfer the fuel to the main tank.<br /><br />TIA<br />JR

 

[JRatliff]

Re: Fuel pumps and Aux. fuel tanks

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