Fuel Tank Configuration

[SeaJay]

I have a small Honda gasoline generator that has an aftermarket auxillary gas tank. The set-up replaces the factory supplied gas tank cap with a non-vented model. This cap has a fuel line that runs directly into the larger auxillary tank. The auxillary tank sits 1 foot below the generator. When running, the generator pulls from its integral tank. I assume this creates a vacuum which in turn draws from the lower tank. You only fill the lower tank and the thing works like a charm.

Now my question. I would like a similar setup with the diesel in my boat. The intregal tank in the above example would be my "day tank". I would like this tank to remain full at all times to assist with trim, and to act as an "emergency reserve". It would be situated at a slightly higer elevation than the main tank. All fuel would be added to the larger, lower, main tank. Fuel would also return to this lower tank. Primary filters would be located between the two tanks.

I'm thinking that in order for this to work, the day tank would have to be un-vented. I understand this is a no-no. However, if the tank was not entirely full and expansion could be accounted for, would this work? Or would I end up a charred corpse and food for the crabs?

Regards to All,

SeaJay

[BTPost]

All you need to do is plumb, say a 20 USG Tank, into the Fuel Return Line, that then overflows back to the Main Fuel Tank. Then plumb a separate Fuel Line from the Emergency Tank, to a Tee at the Input to the Main Fuel Filter, with Isolation Ball Valves in both lines. The Emergency Tank is filled by the Fuel Pump of the engine, with CLEAN Fuel that has been thru both the Primary, and Secondary Fuel Filters, the Injection Pump, and the Injectors, and is always kept Full, and ready for use by the engine itself. I have used such a Fuel System on my Prime Power Gensets for 35 years, and NEVER had a problem with the Emergency Tank Fuel, even if the Main Tank, is full of Water or Algae or any other contaminants. Works slick, and no extra pumps required.

[SeaJay]

Bruce,

Very clever. This will work perfectly, thanks!

Doug

[BTPost]

Yea, I Thought so, after I had used it for a couple of years...