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  1. #1

    Default 4.3 L V-6 Power Increase

    One of our boating friends has been having problems with his carburetor the past month or so. It is a 2002 in a Maxum. It has the original carburetor, and has been rebuilt a number of times. His mechanic told him he should just replace the carburetor, and he has a Rochester 4 barrel and intake he would put on it for a reasonable price. Tells him it would make his 190 HP a 220 HP engine. Is this true or would other stuff have to be replaced as well; distributor, plugs, etc.? Seems like more than a carburetor and intake would be needed to boost the power that much. Any thoughts are appreciated.

  2. #2
    Join Date
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    Spotswood, NJ, USA
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    Default Re: 4.3 L V-6 Power Increase

    If it is a TKS carb, just replace the carb with a regular one and use a good fuel sep.
    Let`s see, the extra 30 hp comes at a greatly increased fuel cost running the 4 bbl wide open.to make 220 hp.
    Dosent sound that good.

  3. #3
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    Default Re: 4.3 L V-6 Power Increase

    Defiantly worth doing.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  4. #4

    Default Re: 4.3 L V-6 Power Increase

    By "defiantyl" are you in jest, or is spell check acting up again. I was hoping to get some more information as to whether he should do this or not, and reasons whether yes or no. More fuel usage would be a negative, any positives? Can this actually be achieved with just a carb and intake change?

  5. #5
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    Default Re: 4.3 L V-6 Power Increase

    Ugh, here we go again. All you get with a 4 barrel carb is slightly higher top end. We're talking maybe a couple percentage points improvement. Whether you need that is dependent on what the boat is used for. If you are trying to get someplace in a hurry then yes get the 4 barrel. If you spend most of the time pulling the kids around on a tube, then no, you don't.
    Boat engines do not behave like car engines...a car uses less fuel the faster it goes because it has overcome rolling resistance. A boat engine is always pushing "uphill" so increasing speed costs exponentially more fuel/air. Sooner or later you will top out the engine's ability to both suck in more food and push the boat faster.
    So, the answer lies with the user. If the performance has been good with the regular carb, then just buy a new one.
    If the new carb and intake being offered is a bargain and less than the cost of the original-type replacement (that needs no modification to the engine), then it would be OK. It will need timing adjusted too, and a new set of tune-up parts would be in order.
    Practicing the ancient art of ren-ching

  6. #6
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    Default Re: 4.3 L V-6 Power Increase

    And the distributor needs to come out--another source of probleems if it doesn't go back correctly.

    Why not leave her along?

    Jeff

  7. #7
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    Default Re: 4.3 L V-6 Power Increase

    Quote Originally Posted by Docksidemarineservices View Post
    Defiantly worth doing.
    Opps. Spell Check. Definitely worth doing. I have done these conversions years ago. No one ever complained about the extra HP or noticed any major change in fuel usage.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  8. #8
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    Default Re: 4.3 L V-6 Power Increase

    A Quadra-Jet might actually get better gas mileage IF you keep those sewer-sized secondaries closed. The primaries are nice and small for good mileage.

    Jeff

  9. #9
    Join Date
    Apr 2009
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    Long Island, NY,
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    Default Re: 4.3 L V-6 Power Increase

    Agree with this; I have a QJet on my old 4.3 and it performs well and is surprisingly economical. The surge of power when those huge secondaries open is great!
    However keep in mind that there are no new factory QJets since the early 90s for boats. So the guy doing the work has to be able to rebuild it and set it up properly. Nother choice is a Holley 4bbl or Edelbrock 1409... Both can be had brand new.

  10. #10
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    Default Re: 4.3 L V-6 Power Increase

    but the carb has to match the bolt pattern on the intake-qjets are spreadbores where the others identified are squarebores...

  11. #11

    Default Re: 4.3 L V-6 Power Increase

    You can get Holley,Edelbrock,Carter and Demon carbs that are direct Qjet replacements.Now if they are Coast Guard legal or not is another story.The 4 bbl debate is one that goes on in the automotive world also,it all depends on what the owner is looking for.If they are happy with the power and speed get a new stock carb and enjoy,if they are looking for a little more umph out of the hole and a little higher top speed go with the 4 bbl.The only one who can justify the 4bbl upgrade is the owner.

  12. #12
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    Default Re: 4.3 L V-6 Power Increase

    The Edelbrock 1409 marine carb is Coast Guard legal. Not sure the others.

    Jeff

  13. #13

    Default Re: 4.3 L V-6 Power Increase

    Quote Originally Posted by fastjeff View Post
    The Edelbrock 1409 marine carb is Coast Guard legal. Not sure the others.

    Jeff
    I decided to buy a 21 feet boat with mercruiser 4.3 mpi......after all these years having all kind of outboards tested..driving planing......it has being to long since my last experience with sterndrives...last time it was twin volvo penta diesels at 93.....now as an experience engineer and 50 years old i came back and retried the sterndrive experience by mercruiser,,,,,,,,BOAT THAT I APROACHED HAD ONLY 150 HOURS AND IT WAS IN GOOD SHAPE THE PREVIOUS OWNER WAS A BOAT DEALER ,,,,,BUT LET ME SPEAK FROM HURT I WAS TOTALY DISSAPOINTED....MERCRUISER IS PRODUCINC JUNK ,,,IRON CUST RUSTY METALS FROM MIDLE AGE....EVERYTHING IN THIS COSTRUCTION IS RUSTED AND FAILURE.....YOU MERCRUISER PEOPLE ,,YOU ARE USING CAR PARTS IN SEA APLICATIONS ,,,,WHAT A BIG FAIL AND MISTAKE...WAKE UP AND SEE ALL AROUND YOU ANODISE ALOUMINIOUM AND ALOUMINIOUM FOR SEA APLICATIONS HAS INVENTED....FOR YOU MERCRUISER PEOPLE THAT YOU WERE MANUFACTURED IRON CAST MANIFOLDS AND RISERS ALL I CAN THINK IS THAT YOU WERE LOST IN MIDLE AGE......EVEN ALL YOUR PARTS ARE FUNNY LOOKING AFTER COMPARING WITH JAPANESE QUALITY,,,,EVEN ORINGS AND HOSES THAT YOU ARE USING ARE JUNK....CABLES ...EVERYTHING IS A BAD JOKE TO ME HERE.......LISTEN TO MY STATEMENT ...JUST HAVE A LOOK AT JAPANESE ENGINES AT SEA APLICATIONS AND START MANUFACTURING GOOD PRODUCTS CAUSE YOU ARE LOOSING CUSTOMERS EVERY DAY....I WILL SELL THIS JUNK CONSTRUCTION HALF PRICE AND GET MY SELF AN OUTBOARD BOAT AGAIN

  14. #14
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    Default Re: 4.3 L V-6 Power Increase

    now as an experience engineer and 50 years old
    ,,WHAT A BIG FAIL AND MISTAKE...WAKE UP AND SEE ALL AROUND YOU ANODISE ALOUMINIOUM AND ALOUMINIOUM FOR SEA APLICATIONS HAS INVENTED....FOR YOU MERCRUISER PEOPLE THAT YOU WERE MANUFACTURED IRON CAST MANIFOLDS AND RISERS ALL I CAN THINK IS THAT YOU WERE LOST IN MIDLE AGE......
    Ayuh,.... Ya might be an engineer, but yer Waayyy off base with yer thoughts,....

    Aluminum can NOT be used in saltwater,...
    It'll disappear twice as fast as iron rusts,...
    Any Grease is Better,... Than No grease at All....

  15. #15
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    Default Re: 4.3 L V-6 Power Increase

    Its a troll.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

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