Alright boys, I need some help, ideas, maybe an exorcism at this point...

The system: 427’s, Holley (red) electric fuel pumps, Racors before the pumps, fuel pressure gauges at carbs, Edelbrock 1409 carbs. Electronic ignition with rebuilt distributors with new Pertronix units.  I’ve put about 12 hours on this set-up without any sign of what’s currently happening. Tanks at about 3/4 full (filled-up last weekend).

What’s happening: On Friday start-up and idle was normal, and did about 10mins at 1000RPM to open water. About 20mins after getting up on plane, I checked my fuel pressure. Starboard side good at about 6psi, but the port was reading 0-1 psi. Shortly thereafter, the port motor started “bobbing” from our 3000RPM cruise down to 25-2600. “Bob” is the best description as it was like the fuel pump was cutting in and out. Come down to 1500, everything smooths out, and fuel pressure returns. Try to run up again, and the pressure drops again, and shortly thereafter the “bobbing” comes back.

What I’ve done so far:
- Tried running with the fuel caps open.
- Tried running with crossover opened.
- Instead of quality family time at the pool, I spent Saturday changing the fuel filters, disassembling and cleaning both pumps (there was some gunk in the pump screen), and swapping them (port for starboard).

This Morning: Start-up, idle, and 1000rpm to open water was flawless. Did fine at 1500. Went to get on plane, and within a few minutes, the “bob” returned. It would let me run for short periods of time at about 2700, but then wouldn’t even allow that. Required we finish the last hour at 1500 to get home.

This afternoon: Knowing valves can cause weird power issues, I checked those while they were hot. Also confirmed timing was good.  Then I swapped the carbs. At this point, I fully expected the problem to switch over to the starboard engine (thereby making the carb the culprit). But it didn’t. The port motor yet again responded the exact same way.

So now what? It’s not the carbs, fuel pumps, or filters. I also don’t think it’s a problem with the crossover or siphon as the motor responded the same way with every combination of open/closed.

Please help. I’m approaching the end of my pitiful rope.

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So I wanted to come and close the loop on this discussion and bring everyone up to speed on where things stand. This offseason, I tore apart the fuel system from the pick-up to the carb. As Lee now calls it, my NASCAR Winters (tear apsart, rebuild, tear apart, rebuild...). 

The biggest hurdle I had to overcome were conflicting instructions on the electric fuel pumps and Racors. Primarily, the pumps should be BEFORE the final filtering, and the Racors want to be on the vacuum side of the fuel system (in other words, pumps after). I spent a lot of time on the phone with racor and Holley, and discovered a loophole that satisfies both.

First, I wanted to avoid the problem that started all this (clogged anti-siphon), so I added a 100 micron Holley filter between the valve and shut-off on the tank. This also satisfies the pre-filter requirement for Holley. Anything more than 100 before the pump, and it strains the pump and can cause flow issues.

But what about the Racor wanting to be on the vacuum side? Ah - that’s true until you read the fine print and talk to them. For most applications, the Racor should be on the vacuum side, but the big 120gph filter allows more flow and can handle up to 10psi. Since the max rating for my pumps is 7, that is good to go! Plus, that filter has the least pressure drop of all their spin-ons, so I should be right at 6 or a hair below by the time it gets to the carb. 

Of course, if I’m going through all this, adding new filters, and redoing fuel lines, might as well make it look pretty too, right?? A little starboard and a ton of time working on layout helped with that! Finally got fuel in the system today, and only had one little leak. Tightened the clamp, and we should be good to go (knock on wood)

Matt ,

Looks nice

One thing you may want to concider is to use mini hose clamps on your fuel hose connections.

They are narrower than standard clamps which make it possible to double clamp your fuel hoses without running out real estate on your hose barbs

Heres an example (you'll have to zoom in a bit)

Thanks Jeremy - I’ll check those out. After seeing the CG and ABYC didn’t require doubles, I just skipped it, but would like what you did.

How loud are those pumps? The Carters that were on my boat when I bought it were petty loud, I could hear them over the engine anything much below 2,500rpms. Are those diaphragm pumps? Surprised they have a vent tube. 

That’s a nice clean install, I like the rubber floor alot! 

Matt Cowles said:

So I wanted to come and close the loop on this discussion and bring everyone up to speed on where things stand. This offseason, I tore apart the fuel system from the pick-up to the carb. As Lee now calls it, my NASCAR Winters (tear apsart, rebuild, tear apart, rebuild...). 

The biggest hurdle I had to overcome were conflicting instructions on the electric fuel pumps and Racors. Primarily, the pumps should be BEFORE the final filtering, and the Racors want to be on the vacuum side of the fuel system (in other words, pumps after). I spent a lot of time on the phone with racor and Holley, and discovered a loophole that satisfies both.

First, I wanted to avoid the problem that started all this (clogged anti-siphon), so I added a 100 micron Holley filter between the valve and shut-off on the tank. This also satisfies the pre-filter requirement for Holley. Anything more than 100 before the pump, and it strains the pump and can cause flow issues.

But what about the Racor wanting to be on the vacuum side? Ah - that’s true until you read the fine print and talk to them. For most applications, the Racor should be on the vacuum side, but the big 120gph filter allows more flow and can handle up to 10psi. Since the max rating for my pumps is 7, that is good to go! Plus, that filter has the least pressure drop of all their spin-ons, so I should be right at 6 or a hair below by the time it gets to the carb. 

Of course, if I’m going through all this, adding new filters, and redoing fuel lines, might as well make it look pretty too, right?? A little starboard and a ton of time working on layout helped with that! Finally got fuel in the system today, and only had one little leak. Tightened the clamp, and we should be good to go (knock on wood)

Thanks Mike! That floor was actually one of the easiest/cheapest little upgrades I’ve done in the boat. That flooring is what HD sells in the giant rolls. I just got a remnant, glued it to the plywood panels down there, and trimmed it in aluminum “L” pieces. Probably $45 all in. Was a good winter project a couple years back.

The Holley’s are loud. But they become part of the general background noise of the boat. I had Carters at one point which were quieter, but I didn’t like that they weren’t marine. They also showed corrosion really quick, which the Holley’s seem to be resisting. Holley makes a marine and auto version of their pumps (to truly be marine it has to have that return line to the carb). They’re vane pumps that are very easy to disassemble and clean (the bottom comes off and all the serviceable parts are right there).

In a perfect world, I would use the mechanical pumps, but with the closed cooling plumbing, the fuel pump is even harder to get to than normal on these 427’s. The Holley’s were the least of all evils. Mallory and Aeromotive both also make marine pumps to spec for the 427, but are at almost twice the price of the Holley’s. Figured I could work my way up into those if need be, but probably not on account of noise.

I’m really hoping this setup gives me a consistent/steady 6psi at the carb. From time to time, my pressure gauge would bob around a bit, and the Holley guys thought that was due to the pump cavatating and trying to pull (versus push) fuel through the very fine Racor. They thought this setup would quiet the pumps some too, so I’ll be able to report back on that once I hear everything next Friday.

My carters aren't super loud. I mean when my engines are running I don't really notice it at all.

Mike H said:

How loud are those pumps? The Carters that were on my boat when I bought it were petty loud, I could hear them over the engine anything much below 2,500rpms. Are those diaphragm pumps? Surprised they have a vent tube. 

That’s a nice clean install, I like the rubber floor alot! 

Matt Cowles said:

So I wanted to come and close the loop on this discussion and bring everyone up to speed on where things stand. This offseason, I tore apart the fuel system from the pick-up to the carb. As Lee now calls it, my NASCAR Winters (tear apsart, rebuild, tear apart, rebuild...). 

The biggest hurdle I had to overcome were conflicting instructions on the electric fuel pumps and Racors. Primarily, the pumps should be BEFORE the final filtering, and the Racors want to be on the vacuum side of the fuel system (in other words, pumps after). I spent a lot of time on the phone with racor and Holley, and discovered a loophole that satisfies both.

First, I wanted to avoid the problem that started all this (clogged anti-siphon), so I added a 100 micron Holley filter between the valve and shut-off on the tank. This also satisfies the pre-filter requirement for Holley. Anything more than 100 before the pump, and it strains the pump and can cause flow issues.

But what about the Racor wanting to be on the vacuum side? Ah - that’s true until you read the fine print and talk to them. For most applications, the Racor should be on the vacuum side, but the big 120gph filter allows more flow and can handle up to 10psi. Since the max rating for my pumps is 7, that is good to go! Plus, that filter has the least pressure drop of all their spin-ons, so I should be right at 6 or a hair below by the time it gets to the carb. 

Of course, if I’m going through all this, adding new filters, and redoing fuel lines, might as well make it look pretty too, right?? A little starboard and a ton of time working on layout helped with that! Finally got fuel in the system today, and only had one little leak. Tightened the clamp, and we should be good to go (knock on wood)

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