1987 OMC 305 Chevy Quadrajet drips off the primaries

[jhonster]

Hello Cliff.  Long time follower of your work.  I think you're the one with the Pontiac wagon that I copied a build on a 64 Grand Prix to replicate.  At least I think you are.

At either rate.  I'm a lifelong professional mechanic and have been rebuilding quadrajets for decades now.  Bought this boat and had to fix a ton of stuff on it.  Noticed the original carb was dripping off the primary clusters so I decided to rebuild it.  The carb dip they have nowadays sucks, but I used some small tools to try to get the passages clean & it seemed to be ok.  Got a rebuild kit for the local boat store that was a factory Johnson/OMC kit (probably reboxed).  At either rate, I matched all the gaskets & put it all back together.  Note...new OMC marine mechanical fuel pump as well.  Carb still dripped and had to turn the mixture screws out almost like 8 turns to get this thing to idle.  Took this carb off and found another used marine carb (same carb number) boiled it out, cleaned all the passages, swapped the jets & metering rods from the old carb to the newer casting.  Essentially the same thing.  This time the boosters are barely barely dripping.  But, are still dripping.  Float is set to specs on the sheet.  The carb had a sintered brass fuel filter in it.  But the boat also has a nice spin on OMC style fuel filter as well.  Have the mixture screws out a good 6 to 8 turns on this one as well.  Got it to idle at 550-600. Timing is set to specs.  Engine has good idle vacuum.  Great compression.  Got any ideas?  Was going to stick an edelbrock marine unit on this thing if I can't get the Quadrjet to behave.  Thanks in advance Cliff.

[Cliff Ruggles]

Couple of things.  Unless you bought one of my kits NONE of them being sold these days come with the correct Marine high-flow N/S assemblies and the accl pump is often incorrect as well, and the blue seal they put on them are junk.

The smaller fuel inlet seat does lower the fuel level some so a small player in not enough idle fuel, but most likely the idle tubes are plugged up some.

They NEVER used a bronze filter in a Marine unit, they should be using the correct high flow micro-screen filters (cleanable).

My rebuild kits come with the correct float, high flow N/S assemblies, and the correct Marine accl pumps with a lifetime warranty seal and new springs.

You try to "rod out" the idle tubes without removing them, but in most cases they will need removed to be effectively cleaned out and re-sized with a precision drill bit as they are almost always all crusted up and restricted or plugged up........Cliff

[jhonster]

Hey Cliff.  Thanks for the quick response.  How much do you charge to overhaul the carb & do the necessary repairs you think should be done vs. just buying your kits and ness parts to do what you explained?  Whats shipping like from Mt Vernon to Los Angeles?

Ran a few tanks of fuel running the boat on the ocean.  Its actually running fairly decently.  Although if I remove the spark arrestor, I can see it still dripping a few drops here and there barely.  It was much much worse before the rebuild.  Most of the quadrajets I've adjusted over the years only required bringing out the mixture screws 3-4 turns.  I've opened up the mixture screw holes in the past with thousandths drills I have, and it seemed to aleve past carbs I've worked on.  Not sure if I'll need to do that on this unit.  Because if the carbs dripping now, it means its running slightly rich at idle already.  If I fix the dripping problem, Im guessing I'll be on the lean side.  What do you think?

[Cliff Ruggles]

I charge $225 labor plus parts/shipping for Marine carburetors.  Have done thousands of them at this point and pretty piled up with them at the moment because a lot of folks have their boats in storage this time of year. 

Cool story but recently had a customer not too far from here build his own carbs with parts store kits, pretty sure he got them at NAPA.  They didn't work for chit from day one and after one outing they refused to re-start without pouring some fuel into them to prime the engine.

He hand carried them here, I tore them apart right in front of him.  One accl pump seal was torn, the other stuck so hard in the bore I pulled the cheap plastic pump apart trying to pry it out!  They N/S assemblies had a tiny little hole in them instead of the correct .135" high flow units.

The idle tubes were plugged solid, couldn't even rod them out had to removed them.

I put in the correct Marine parts, set the float height, and they were flawless.  Happens all the time if you use the correct parts, settings and get the idle tubes opened back up.

I actually open them up a little bigger than the factory sizes because of this new fuel having less energy that what they were originally tuned for.  Never had the first complaint and it gives them the fuel they need at idle so you don't end up backing up the mixture screws till they just about fall out of the carb to make the engine happy!.......

[Cliff Ruggles]

PS:  you may also notice two other things about that pump.  It is NOT the correct length Marine length pump and the spring on it is some imported POS that coil binds when the pump is compressed....very bad!

Marine pumps are very short for a good reason.  Marine engines are heavily loaded and when you are applying throttle to get thru a no wake zone (for example) and you decide to go ahead with the throttle quickly to come up on a plain a long pump is already used up and you will NOT have any pump shot left. 

This causes a noticeable stumble/hesitation/bog and often the engine may stall out.  The factory knew this and why the accl pumps in Marine carburetors are much shorter than all others.......