General Category > Quadrajet Carb Talk and Tips

Fuel pressure issue? or volume issue? in a Boat.

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Kenth:
I have yet seen a marine Quadrajet with large bore primaries, no such animal.
Unfortunately sounds like you´ve got a "frankencarb" car quadrajet from the "remanufacturer" instead of a correct marine unit, thus your issues.

Pale Rider:
my files are to large so I couldnt post a pic... as mentioned the rochester runs great. the issue is with both the holley and the previous test prior to the Holley on the Rochester. truth be told this rocky runs like a beast up until the demand is high after 43-4400 rpm. not a problem planning off in this heavy gal. I have to agree, the shop built something from something and the bump in the correct position is indeed there. crap I was excited to see this, lolol, anyway I`m still looking for the pressure and or volume drop cause.

Kenth: I don`t doubt at all what your saying. the original had a divorced choke whereas the one I have now is electric choke. I do not usually mess with Rochesters, and most of the mercruiser`s Ive seen or worked on were Rochesters or Carter/Weber/Edelbrock.

Cliff Ruggles:
Now we are getting somewhere, but I hope your sitting down when you read this.

You have a "remanufactured" carburetor not a "professionally built" unit.  You should have kept your original and had it completely/correctly rebuilt instead.  If that were the case you would very quickly be able to isolate your issues between the carb and fuel delivery...FWIW

I haven't seen a Frankencarb Marine unit to date that was worth two squirts of duck poop, or even had Marine rebuild parts in them, and that includes unit from I-5, National and where you got yours from.  Sure they sell gobs of them, but they are NOT Marine units or do they even really know what to use in them or how to calibrate them for a Marine application.  Those "generic" calibrations they use, driving lead plugs in holes, hacking up/smashing down the idle airbleeds, driving in restrictors, trying to resize MAB's, and the list goes on and on and on ends up with a product that from my observations and testing is a complete pile of bovine excrement.

I don't say any of that to make money or steer any work in my direction, I'm too busy as it is and retired in April.  For the record I'll still be selling parts 2-3 more years and doing a couple of carbs a week for the Bourbon fund, but NO MORE restorations, bottom of the farm pond resurrections, or hacked up junk wanted.

As far as your "Marine" remain, I will just say that I've had scores of them sent here when folks thought they were sending me a "Marine" carburetor and I will NOT rebuild them.  Instead I source out a real Marine carb instead as it will be a home-run every single time when completely/correctly rebuilt using the correct parts.

I just did this for a customer in Washington state after he inadvertently sent me two POS remanufactured Marine carbs that were on the boat he just purchased.  They a MESS, right down to the dog-leg vent tube that blocks incoming air and sits right over one of the MAB interrupting it's function.  I had him source out two original Marine units off of Ebay (different part numbers) but I built him two identical units for his engines and good to go.

So basically if you want help with this project you'll need to locate a correct Marine carburetor and completely/correctly rebuild it.  I'm betting ALL the problems will go away at that point and you'll be able to run a mechanical fuel pump with stock filters, lines, etc........Cliff

Cliff Ruggles:
PS:  The "blanket" statements from your sources about how much fuel pressure a Quadrajet needs are still inaccurate.

I don't want to write another book here, but there are a LOT of variables involved with fuel control, fuel pressure, float size, type of carb (hinge pin location), size of the float, type of float (brass or closed cell nitrophyl) and size of the hole under the needle.

If you don't understand any or all of that, and messing around with different models, small brass floats, and different N/S assemblies the result will be ALL OVER THE MAP, hence most likely why we see so much varying information posted out there on the subject........Cliff

Pale Rider:
Cliff, agreed,  yes I understand all that. I immediately saw the cross breeding when I received my reman carb from Guaranteed carburetors. and yes I should have kept my carb that came with the boat, even though I was not 100% sure it was original or not. when I installed the 350 repower into the boat a new Holley was also installed, hence the comparison conversation. The current issue is with either Carb. 1 new, 1 reman, same results.
Your honest information was what I was seeking in moving forward. It would seem its even hard to trust products right out of the box from New Carbs to remanufactured carbs these days. I have seen other companies install the dog leg vent tube in the same exact locations and questioned its position from other brands out there.
Thank you for the tutorial and information. I`ll get this sorted out.  8)

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