Tuning a Rebuilt Marine Quadrajet on a Mercruiser 305

[ddkjunior]

Hello,

I recently purchased a 1984 Cobalt boat with a very low hours Mercruiser 305 that is in great shape...in fact the engine serial numbers indicate it is from the early 1990's and must have been replaced.  I rebuilt the Marine Qjet that was gummed up from sitting and had two issues:

1.  VERY big flat spot on hard acceleration...appears to be when the secondaries open.
2.  Hot start was difficult on a couple of occasions...appears to have flooded after sitting.

I replaced the carb with an identical rebuilt unit and have the same two issues to a lesser degreee.  Any advice would be appreciated.

[Cliff Ruggles]

Hopefully you still have your original unit?

Did you use one of our kits for the "rebuild"?

Did you replace the secondary cam and spring during the rebuild?

Did you replace the choke pull-off?

Was the main casting pressure tested for leaks at the bottom plugs?.....Cliff

[ddkjunior]

Yes, I still have the original unit - it's in excellent condition so I plan to rebuild again...properly this time...bought your book, etc.

The answer is no to the rest of your questions...I was hoping the rebuilt carb would take care of things.

Tell me what I need to order to take care of business....Thanks.

[Cliff Ruggles]

I haven't had a commercial "remanufactured" or store bought carburetor sent in here in at least 10 years that was worth two squirts of duck poop!  Just got off the phone earlier today with one customer telling him the unit he sent here for us to build was from an auto parts store, and nothing but a POS, nothing we can do about it.  I have to make the same call again this afternoon on another "reman" we opened up this morning.

They are all just hacked up factory units with "generic" calibrations, crappy parts, incorrect settings, mangled up/mixed up/busted up and never anywhere near where they need to be.  Very, very rare if they work well, or even work at all.

Spend your time/funds on the original unit, or obtain a "virgin" core and spend the efforts there.  As good as I am at this deal, I absolutely HATE to see any remanufactured units come in here.  There are ALWAYS the most work, and poorest results. 

Anyhow, for what you are doing, put one of our kits in the original unit carefully following the guidelines in our book.  Verify the casting isn't leaking at the bottom plugs, make the correct settings, new cam/spring, and it will work just like it's supposed to......Cliff

[ddkjunior]

Thanks for your advice...just by chance I recently purchased an Edelbrock 1902 that is used but in pristine condition.  I was going to put it on a Jeep but I assume it may be a good candidate for the boat as well? Your thoughts?

If I do put it on my Jeep, it's going on a 304 V8 with a new Edelbrock Performer manifold.  Since this has no provisions for the divorced choke should I just ditch the choke altogether?  I live in a warm climate and the Jeep is just a toy, not a daily driver.

Thanks again.

[Cliff Ruggles]

Two completely different applications.  The 1902 came in several "flavors" and will need recalibrated for Marine use.

Marine engines operate at heavy load and low vacuum, and the carburetors on them were not emission calibrated, or lean anyplace.

I'd use it on the Jeep, and the Marine unit on the boat.  The Marine unit also has the fuel pump overflow or should have, and the correct linkage for Morse control......Cliff