fuel Manifold

Drake said:

Go on Yachtworld and look at listings for Defever 44, 49 and 50. They all have very good fuel manifolds. I'd post a pic of mine but for some reason I can't post from my iPad.

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Yup, great manifolds - another thing Art did right. I have a Groco fuel transfer pump on the manifold which permits movement of fuel between 4 tanks. Albeit at a low rate of 3 gpm.

The fuel returned to the tank is for cooling the injection pump. All that compressing of fuel to inject it creates lots of heat. To stop the fuel boiling and cavitating lots of fuel is run through the system and returned to the tank. The return circuit is almost more important than the supply circuit, unless your tanks are not fore and aft but side to side, then "usually" a large connecting pipe between the two tanks allows for the fuel to migrate to its own level.

Xsbank said:

The fuel returned to the tank is for cooling the injection pump. All that compressing of fuel to inject it creates lots of heat. To stop the fuel boiling and cavitating lots of fuel is run through the system and returned to the tank. The return circuit is almost more important than the supply circuit, unless your tanks are not fore and aft but side to side, then "usually" a large connecting pipe between the two tanks allows for the fuel to migrate to its own level.

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Depends on the engine. Some like Lehmans return very little fuel.

Engines that return a lot of fuel usually have inline fuel coolers because with out them the returned fuel can heat the whole tank of fuel up and the fuel in the tank just gets hotter and hotter. Especially as the level goes down in the tank and the volume of fuel is reduced.

All diesel-burning engines, even jet engines, return fuel to the tank. Lots of fuel-injected cars do too, I'm not sure if for the same reason.

Xsbank said:

All diesel-burning engines, even jet engines, return fuel to the tank. Lots of fuel-injected cars do too, I'm not sure if for the same reason.

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Not all. Some MTUs don't.

Xsbank said:

The return circuit is almost more important than the supply circuit, unless your tanks are not fore and aft but side to side, then "usually" a large connecting pipe between the two tanks allows for the fuel to migrate to its own level.

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So oddly enough I could not for the life of me figure out why my boat kept listing further and further to stbd after I bought it. I asked the PO about it, and he said, no it's gotta be the water tanks making it lean.

Sure enough, it turned out that the fuel tanks werent balancing at all. The port was siphoning into the stbd tank. A little siphon action and the boat would list, then the tank notices hey, he's got more than me "because he's higher than me", and a little more siphoning action.

By the time I got around to shutting off the valves it was getting to where I was wondering when it would just roll over.

albertldee said:

hi don't know if there is any experience fuel manifold specialist could help me design a fuel manifold material is not a problem just want to design something simple

this is what I have

2 tank AFT & FWD each tank have 1 feed only
2 pump AC and DC

what I would like to do is to have the AC pump suck and transfer to either tank
Likewise the DC pump to suck and transfer to either Tank

if I get a drawing I can follow the instruction

thanks in advice busting my brains here trying to figure it out and make it simple

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There are some drawings and equipment specs here: Fuel Polishing - delfin.talkspot.com

I had my manifolds made up for about $50 by a local shop. The a/c motors using carbonator pumps run quietly as opposed to DC pumps that are noisy, can be sized for any flow rate, and will run continuously, which is also something DC pumps don't do well.

Well done, Bill, I concede. You are right, Some MTUs recycle their fuel back through a cooler and back to the injection pump. I give up.

Xsbank said:

Well done, Bill, I concede. You are right, Some MTUs recycle their fuel back through a cooler and back to the injection pump. I give up.

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Sorry I didn't mean it to come off like I was trying to put your knowledge down. Just pointing out you can't generalize that all diesels return a lot of fuel to the tank and that some in fact don't return any at all.

You and I may know that but some here may not.

I've kind of stayed out of this because in post five the op says he has no return lines. That seemed unlikely to me. I didn't know MTU engines didn't have a return line.
Before we can help him I think we need to confirm that he has no return lines. We also need to know if he has a single or a twin engine boat or did I miss that?