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Author Topic:   Fuel Plumbing Question

Buckda posted 08-18-2010 03:48 PM ET (US)
My boat has two in-deck tanks and twin 130 HP carburated V-4 OMC's.
I'd like to add a portable on-deck tank plumbed into the fuel system.
Right now, the plumbing goes like this:
Tank 1 and Tank 2 feed into a selector switch (1,both,2,off settings). From the switch, the line feeds into a manifold that distributes the fuel into two 3/8 ID hoses that both lead into a single fuel RACOR filter manifold, and then there are two lines that exit the filter and feed each motor through separate primer bulbs.
I'd like to add a "T" fitting to one of the lines that goes into the fuel filter manifold AFTER the distribution manifold on the switch. This T fitting would lead to my on-deck tank and have a shutoff valve on it to effectively seal the line when not in use.
In this setup, I could shut the main under deck tanks to "off" and just draw from the on-deck tank. When it empties, I'd be able shut off the on-deck tank and select one of the belly tanks to resume operation as normal.
Any thoughts as to doing it differently? All lines would be 3/8" ID - the same as is currently on the boat.
contender posted 08-18-2010 04:45 PM ET (US)
Separate fuel line and connect it right to the engine, or put your tee at the engine connection(with a shut off then you can remove the tank when not in use), use/have a shut off for the main tank and would just suck fuel out of the on deck tank....good luck
Buckda posted 08-18-2010 04:56 PM ET (US)
Here's an illustration for what I'm thinking.
http://www.facebook.com/photo.php?pid=31625863&l=3d5b18c4af& id=1383963684
The fuel lines are plumbed directly into the engines, so I can't just disconnect the main tanks at the engines...plus, there are two engines, so how would you do that with an auxiliary tank?
I realize now that I didn't label the tanks - in my illustration, but the top two represent the twin 70 gallon belly tanks and the third one down represents the auxiliary tank.
Dave
Buckda posted 08-18-2010 04:58 PM ET (US)
From the brass T fitting back to the third tank would be "new" plumbing the rest is original.
Realize that in the long term, this system will be re-plumbed to accomodate a second fuel filter...for now, I'm "stuck" with that portion of the setup and it won't be changed for this project.
Dave
contender posted 08-18-2010 09:45 PM ET (US)
Bucka: You can just put the tee where the brass manifold is and elimate some connections and the manifold. Just have another shut off for the third tank...
Jerry Townsend posted 08-20-2010 12:38 PM ET (US)
Dave - Your plan - and the suggested modification by Contender will work.
My only comments - 1) use the largest diameter lines and components possible to reduce the friction and improve the fuel flow, and 2) consider using ball valves - better sealing, you do not need "throttling" capability and faster operating - but a bit more expensive. ---- Jerry/Idaho
Jerry Townsend posted 08-20-2010 12:42 PM ET (US)
Dave - damn - I meant to mention one more item - when possible, plumb your lines so that the normal fuel flow is via the straight thru tee run - rather than the branch tee run - -- just guves less flow restriction and resistance. --- Jerry/Idaho
Buckda posted 08-20-2010 12:54 PM ET (US)
Thanks guys. The T fitting came in the mail today. I will be rigging this over the weekend.
Dave
Buckda posted 08-23-2010 10:15 AM ET (US)
Rigged and no leaks. Thanks for your thoughts!

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Author	Topic: Fuel Plumbing Question
Buckda	posted 08-18-2010 03:48 PM ET (US) My boat has two in-deck tanks and twin 130 HP carburated V-4 OMC's. I'd like to add a portable on-deck tank plumbed into the fuel system. Right now, the plumbing goes like this: Tank 1 and Tank 2 feed into a selector switch (1,both,2,off settings). From the switch, the line feeds into a manifold that distributes the fuel into two 3/8 ID hoses that both lead into a single fuel RACOR filter manifold, and then there are two lines that exit the filter and feed each motor through separate primer bulbs. I'd like to add a "T" fitting to one of the lines that goes into the fuel filter manifold AFTER the distribution manifold on the switch. This T fitting would lead to my on-deck tank and have a shutoff valve on it to effectively seal the line when not in use. In this setup, I could shut the main under deck tanks to "off" and just draw from the on-deck tank. When it empties, I'd be able shut off the on-deck tank and select one of the belly tanks to resume operation as normal. Any thoughts as to doing it differently? All lines would be 3/8" ID - the same as is currently on the boat.
contender	posted 08-18-2010 04:45 PM ET (US) Separate fuel line and connect it right to the engine, or put your tee at the engine connection(with a shut off then you can remove the tank when not in use), use/have a shut off for the main tank and would just suck fuel out of the on deck tank....good luck
Buckda	posted 08-18-2010 04:56 PM ET (US) Here's an illustration for what I'm thinking. http://www.facebook.com/photo.php?pid=31625863&l=3d5b18c4af& id=1383963684 The fuel lines are plumbed directly into the engines, so I can't just disconnect the main tanks at the engines...plus, there are two engines, so how would you do that with an auxiliary tank? I realize now that I didn't label the tanks - in my illustration, but the top two represent the twin 70 gallon belly tanks and the third one down represents the auxiliary tank. Dave
Buckda	posted 08-18-2010 04:58 PM ET (US) From the brass T fitting back to the third tank would be "new" plumbing the rest is original. Realize that in the long term, this system will be re-plumbed to accomodate a second fuel filter...for now, I'm "stuck" with that portion of the setup and it won't be changed for this project. Dave
contender	posted 08-18-2010 09:45 PM ET (US) Bucka: You can just put the tee where the brass manifold is and elimate some connections and the manifold. Just have another shut off for the third tank...
Jerry Townsend	posted 08-20-2010 12:38 PM ET (US) Dave - Your plan - and the suggested modification by Contender will work. My only comments - 1) use the largest diameter lines and components possible to reduce the friction and improve the fuel flow, and 2) consider using ball valves - better sealing, you do not need "throttling" capability and faster operating - but a bit more expensive. ---- Jerry/Idaho
Jerry Townsend	posted 08-20-2010 12:42 PM ET (US) Dave - damn - I meant to mention one more item - when possible, plumb your lines so that the normal fuel flow is via the straight thru tee run - rather than the branch tee run - -- just guves less flow restriction and resistance. --- Jerry/Idaho
Buckda	posted 08-20-2010 12:54 PM ET (US) Thanks guys. The T fitting came in the mail today. I will be rigging this over the weekend. Dave
Buckda	posted 08-23-2010 10:15 AM ET (US) Rigged and no leaks. Thanks for your thoughts!