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Fuel line routing - electric - bypass to tank or filter head?

Old 04-01-2021, 10:12 PM
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Default Fuel line routing - electric - bypass to tank or filter head?

I'm going to have more of these questions coming about as I re-rig a lot of things for the new builds.

I'm forced to go electric for the fuel pumps. I wish I could run mechanical pumps, but with the Gen-VI set-up, it's not happening.

In between what seems to have been an endless number of process meetings, I've been reading and checking out pics of engine-mounted pumps. For the ease of packaging and tp prevent drilling holes into my old 311, I'm going to mount the pumps on the engines using the filter heads as the gravity feed for the pumps.

My question has to do with the bypass return. The MPI/Cool Fuel set-up routed fuel back to the filter head. I've upgraded the filter head to use larger 3/8 NPT fittings, and have thought about routing the return in the same way. Will that work to prevent any vapor lock or will I need to route it all back to the tank to keep the fuel cool? I'd rather use the filter head as a return for packaging purposes, but I can go back to the tank if it's necessary.

Also, what about push-lock hoses all the way to the carbs? I can get USCG-rated hose to do the job, but is legal? I was going to use braided stainless (I know it's not "legal") but I like working with the push-lock stuff.

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Old 04-02-2021, 11:13 AM
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Hose on engine has to be rated A1-15:

see:
https://newboatbuilders.com/pages/fuel.html

and:
https://www.uscgboating.org/assets/1...YC.1002.01.pdf
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Old 04-02-2021, 11:31 AM
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Thanks! A quick read says the A1-15 can be used overall - so that works.

Is my thinking on the routing okay? I read about some vapor lock issues some had where it was fixed by routing back to the tank.
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Old 04-02-2021, 11:49 AM
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Low psi carbureted with a low psi carb electric pump should be okay deadheaded with no return.

What kind of system , fuel pump and psi are you going to tun ?
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Old 04-02-2021, 11:57 AM
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Holley Blue pump to a Demon 850. 7 PSI max. -8 from tank to filter head/separator to pump to carb. I was going to run in bypass to keep the pump from burning up.
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Old 04-02-2021, 04:38 PM
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Mounted on the engine are they going to be lower than the tanks or how is that going to work , them pumps don`t like to suck, mine are mounted below tanks.
You can do return to filter with that low pressure but would back to tank be better , yes.
As I learned on an episode of Engine masters , hot fuel is less power , cool fuel is better even more so than an iced intake.


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Old 04-02-2021, 04:59 PM
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My Whipple kit came with an electric fuel pump, and they route the return to the filter head. It goes through a fuel cooler before it goes into the filter head FYI.
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Old 04-02-2021, 07:33 PM
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https://www.cpperformance.com/p-7398...ater-pump.aspx

ouch 600 bucks a piece, i was wondering why your using electric pumps to carbs when you prefer mechanical.
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Old 04-02-2021, 11:49 PM
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Routing back to the tank should work but last resort. First try preventing heat from the motor from getting to the fuel line simply by insulating the line and this may solve the problem and not have to run it back to the tank. Worked on my boat that had severe vapor lock.

But i also found that the fuel line was running close to the bottom of the oil pan. So i just insulated the line and also put a small sheet between pan and line. All vapor lock issues gone, no return needed. Easy to try. Alum bubble wrap at Lowes.
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Old 04-03-2021, 07:45 AM
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Originally Posted by ICDEDPPL View Post
Mounted on the engine are they going to be lower than the tanks or how is that going to work , them pumps don`t like to suck, mine are mounted below tanks.
You can do return to filter with that low pressure but would back to tank be better , yes.
As I learned on an episode of Engine masters , hot fuel is less power , cool fuel is better even more so than an iced intake.
I was going to mount the pump similarly to the original MPI pump. That would put the pump lower than the outlet of the filter. The siphon effect would then keep the pump fed. I donít have a problem sending the return back to the tank. My 311ís tank has return bungs already. I thought the filter head as a return would clean up the installation some, but Iíll follow best practices. Fuel back to the tank will stay cooler vs circulating around the hot engine.
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