Ask SAIL: Leftover Gas in Tank

I have two 6-gallon gas tanks on my 25-foot O’Day, but when the motor quits and I have to switch tanks, there is still about 1 1/2 gallons left in the “empty” tank...

Author:: Nigel Calder
Updated:: Aug 2, 2017
Original:: Apr 10, 2014

ADAM LAWALL, CLINTON TOWNSHIP, MICHIGAN

Q I have two 6-gallon gas tanks on my 25-foot O’Day, but when the motor quits and I have to switch tanks, there is still about 1 1/2 gallons left in the “empty” tank. What is causing this, and what can be done about it? Could it be the setting of the air intake?

Nigel Calder Responds

A My guess would be the suction lines are set an inch or so off the bottom of the tanks to avoid drawing in any water or sediment that might collect there. This is a common practice with marine fuel tanks. Typically, the tank is much larger, so leaving 1 1/2 gallons on the bottom has little impact on overall fuel availability. However, with your small tanks it is obviously a significant percentage of the available fuel.

NigelCalder

Nigel Calder is an author and expert on boat systems and diesel engines

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