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Thread: How can you tell if an engine is counter rotation?

  1. #1
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    How can you tell if an engine is counter rotation?

    I'm looking at some engines and they are a pair that came out of a Cigarette. Not sure if one is counter rotation. Is there a way to tell by looking at them on stands? They are 420 Mercruisers.

    Any help would be great!

    Scott Pearson
    President, Lake George Donzi Classic Club
    www.lgdonziclassic.com

  2. #2
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    Pull the valve covers, crank by hand, watch intake valves for firing order?

  3. #3
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    When you put it in reverse and the bow slams into the dock??

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    Check distributor wires for which direction it's spinning to get the right firing order.
    Maddy's Daddy
    L.I.,N.Y.

  5. #5
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    Quote Originally Posted by mattyboy View Post
    When you put it in reverse and the bow slams into the dock??
    +1

    Ken

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    fastest visual..

    inlet and outlet hoses on the sea water pump shouldn't match

    starter drive teeth angle shouldn't match

    harmonic balancer timing marks / tabs shouldn't match
    Charter Member - WAFNC, SBBR, KWOSG
    1955 Perfect Mate
    1986 Hornet III, 502-415 TRS

    www.donzi.org


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    Scott if they were stern drive engs matted with trs drives and trans there both lefty's
    mario

  8. #8
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    Firing order on the cap. On inboards with Velvet drives The starter is usually bolted on backwards "aft of the engine". I do not believe that there has ever been a reverse rotation Stern drive. But the firing order is truly the best way to tell. Or jump the starter and see which way it cranks
    machinist ,bore it deeper,ream it bigger, and lap it to a fine finish



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  9. #9
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    Remove the timing cover and look for a gear drive w/an idler to reverse cam rotation.
    George Carter
    Central Florida
    gcarter763@aol.com
    http://kineticocentralfl.com/


    “If you have to argue your science by using fraud, your science is not valid"
    Professor Ian Plimer, Adilaide and Melbourne Universities

  10. #10
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    Thanks for the great info guys. I missed out on these engines...I need to start looking again for a BBC. This guy had 2 and I figured I would buy both.

    Scott Pearson
    President, Lake George Donzi Classic Club
    www.lgdonziclassic.com

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