Vortec 4.3 cracked block ... automotive swap?

Discussion in 'Gas Engines' started by carolinaXJ, Apr 14, 2012.

  1. carolinaXJ
    Joined: Apr 2012
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    carolinaXJ New Member

    I've researched and researched some more on swapping a mercruiser vortec 4.3 with a GM vortec 4.3 but can't find the answer to wether it can actually be done or not. Ive found a few threads of people asking this same question but once they ask the question everyone seems to have a different opinion and the original poster never replies back as to wether it was possible. So can it be done or not? Im curious as to the cost also if anyone has had experience doing this. Any and all help is much appreiciated!!
     
  2. mariocroatia
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    Location: dubrovnik croatia

    mariocroatia Junior Member

  3. carolinaXJ
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    carolinaXJ New Member

    I found a local guy on craigslist that will sell me a 4.3 vortec block for $100 so i'm trying to see if its possible and if I can save any money, thats the point
     
  4. mariocroatia
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    mariocroatia Junior Member

    no hard feelings ,u are saving money compering our example, if u r like me from europe....
    im not realy shure but i think its the same block ....
     
  5. IMP-ish
    Joined: Jan 2011
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    IMP-ish powerboater

    What year is your mercruiser 4.3? Find the serial number & year on the block.
    Mercruiser has used GM blocks for years.
    Make sure your heads will fit; vortec or pre-vortec 4.3.
    Swap over marine carb, starter, alternator, bell housing and all other marine bits. No problem.
    With high performance engines you have better marine cams.
    Long block
    you've got corrosion resistant exhaust valves in marine engines.
     
  6. carolinaXJ
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    carolinaXJ New Member

    The boat itself is a 1997 but I will look at the block tomorrow and try to find the numbers, thanks!!
     
  7. CDK
    Joined: Aug 2007
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    CDK retired engineer

    I'm glad you noticed this strange phenomenon with original posters not responding.

    Go for the $100 block, but check the bearings and cylinders before reassembling.
    And make sure to paint the olive green black, because that's the main difference between a GM and a Merc engine.
     
  8. missinginaction
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    missinginaction Senior Member

    Well said CDK! :)
     
    1 person likes this.
  9. gonzo
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    gonzo Senior Member

    There are other differences. For example, the alloy in the marine engine is more corrosion resistant than the automotive version. It makes a huge difference in direct cooled engines. The valves, depending on the model, may be different alloy too. The harmonic balancer and flywheel are different too. The oil pump has a different spring. The automotive block, unless it is a very early model without counterbalance shaft, will not have a place for the mechanical fuel pump. That means it needs a proper modification with an oil pressure shut-off switch.
     
  10. Frosty

    Frosty Previous Member


    Oh dear, is that the alloy of the block. you think they cast marine blocks at the foundry?

    If its a 4 bolt mains its a marine block as used in the marine industry.

    Who has raw water cooled engines anyway.

    A high torque 4 wheel drive application inlet manifold is better than any marine, blanking off any TCV or EGV is easy.

    4 wheel drive cam is also the way to go torque torque torque and get one that fits with the inlet manifold and get a package,--thats the way to make HP.
    Fuel pump? well use electric. its not rocket science but what is day light robbery is marine.
     
  11. IMP-ish
    Joined: Jan 2011
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    IMP-ish powerboater

    Guys who don't want to spring $900 for a merc closed cooling kit.
     
  12. gonzo
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    gonzo Senior Member

    The alloys are different, you can identify them by the casting numbers. Throughout the 80's all Nascar blocks were marine castings to comply with the "factory standard" rule. They found out that the extra nickel makes them less likely to crack.
     
  13. carolinaXJ
    Joined: Apr 2012
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    carolinaXJ New Member

    I didnt get a chance to get the numbers today but I am meeting the local guy tomorrow with the $100 block, my plans right now are to try and tackle this thing over the next few weeks and take some pictures and make a how to thread for other people with the same questions and problems. Hopefully all works out well, thanks for all the help and quick responses, ill keep this thread updated as to wether things are going good or I get frustrated and find a cheaper hobby!! Thanks!!
     
  14. Frosty

    Frosty Previous Member

    Ive never seen a raw water cooled motor except on DIY kubota jobs.

    If you run lakes and rivers you might be able to get away with it.
     

  15. gonzo
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    gonzo Senior Member

    I guess you haven't been to North America. The majority of engines for small boats are raw water cooled.
     
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