Fuel Return Question On Repower

[Mike P]

I am in the process of repowering a gas boat to Cummins 370’s. The boat has two tanks, one on the outboard side of each engine. The existing plumbing utilizes a manifold system so that either tank can supply either engine. I like being able to occasionally switch from one tank to the other in order to maintain equal amounts of fuel in each tank. I realize I will need to make a new manifold system that can handle more fuel flow. My thought was to convert from the current 3/8″ to 1/2″ lines and manifold. From reading on this site, I was planning on having the fuel return lines set up with no shut-off so there was no chance of return fuel backup. So, two questions. 1) Is there an accepted way of plumbing the returns so that fuel is returned to the tank it is drawn from? 2) Will the 1/2″ lines and valves be adequate to supply fuel from one tank to both motors at the same time? Appreciate any other suggestions or observations that I might be overlooking.

Topic

[Mike P]

Thanks Tony, I have read that and will remember it.

[Tony Athens]

Use 1/2″ ID fuel line for the supply ——-I consider that is a minimum for this engine as fuel flows ( for all intents & purposes) about 1 Gallon per minute at all times & RPM’s …………………

Never, and I mean never have a return line shut, for even a 1/2 second with the engine running..

Assume that you are returning fuel to a tank at close to 1 gal per minute per engine , so plan your fuel supply system around that..

Tony

[john]

You can probably get away with 3/8 but I would go with 1/2 inch. You don’t see a return at the same point as the supply on most diesel installs.

[Mike P]

Might have found the answer

After more internet search time, I may have found the answer to my question. Groco offers a 6 way fuel valve that offers the ability to change tanks for both the supply and the return sides simultaneously. This valve is available in a couple different sizes so I am still interested to hear what size I should use.

[Author]

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