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  1. #1
    Just Say N2O

    Question Engine wizards, spark plug question

    Closer plug (split-fire) is from port engine w/about 60 hours. Both engines are Crusader 270 hp Chevy 350s, w/Rochester QuadraJet Carbs.

    Farther plug from starboard engine w/about 25 hours on them. All the split-fire plugs looked the same, as did all the others.

    Bought a Carb rebuild kit. Think this will cure my problem?

  2. #2
    Just Say N2O
    Where's the picture?
    Attached Images Attached Images

  3. #3
    bobby daniels
    Maybe but you need to compare apples to apples ,compare the same heat range and type plugs ! Cut the ground off the plugs they will most likly run the same as split fires and other exotic plugs,don't waste your hard earned cash just buy go old plugs,if you want race or trick plugs you can cheat and file or cut the ground strap back half backacross the center electrode ,that will help

  4. #4
    Just Say N2O
    I actually ran the same Champion plugs in both engines the season before, and the result was the same. Obviously, I fell prey to some sweet talking salesman regarding the SF plugs. Didn't notice any difference in the performance of the engines, but at least the plugs were 3X $.

    These engines are in a 31' Wellcraft Express Cruiser, so it isn't a "high performance" issue. More of a keep the engines running correctly issue.

  5. #5
    bobby daniels
    Yep use a good set of a/c (just my preference) like 44 heat range and install that kit ,,,good luck

  6. #6
    Offshoreonly Advertiser Offshoreonly Advertiser
    My Boats:
    Join Date
    Jan 2001
    spring valley,ny usa

    quadrijet carbs

    Don't forget to install new floats,these floats gain a few grams in weight after a few years and the needle does not seat properly.

  7. #7
    Just Say N2O
    I haven't got them apart yet, but was told the marine carbs have brass floats. Should I still have to replace the floats?

  8. #8
    bobby daniels
    no not as long as old one is dry inside and not in bad shape

  9. #9
    Charter Member Charter Member Ted G's Avatar
    My Boats:
    Marlago 35 FS, 18 Neptune CC
    Join Date
    Jan 2001
    Edgerock Baby!!
    If that is the only plug that looks like that it is not the carb, you say all the others look the same-do you mean as the SF?? If that is the only plug doing it you may have bad valve seals in that cylinder. If not those then bad rings-bad juju. A compression and /or leakdown test may be in order if that is the only dark plug. If they are all the same in that motor then a carb kit may help. If it has a brass float then shake it and see if there is liquid in there-if not you can reuse it. If they are foam replace them. Also get some epoxy and fill the area beneath the bowl where you will se a little nipple with 2 small plugs in it. The plugs fill holes that are drilled into the bowl and begin to leak when the carb gets older-this can cause rich running and hard starting after sitting a while due to carb bowl leakdown. Once you get the carb rebuilt and sealed make sure you do all the adjustments in order-paying special attention to the secondary air flap adjustment-if the flaps are too loose it can run rich and have a feirce bog on acceleration-this is what gave the carbs a bad name back in the day-it was really the guy tuning them, not the carb. In fact the air flap adjustment properly done will make a Quad run with any carb out there.
    Chesapeake Bay Powerboat Association

  10. #10
    Just Say N2O
    Thanks for the information. All eight of the plugs from the starboard engine look like the Champion, and all the plugs from the port engine look like the SF pictured. I should have mentioned that in the initial diagnosis request.

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