Reverse rotation timing

Discussion in 'Gas Engines' started by silkuk, Aug 24, 2008.

  1. silkuk
    Joined: Aug 2008
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    Location: Alaska

    silkuk New Member


    I've got a dual 350 inboard setup with the port engine being reverse rotation. When I set my timing should I use the opposite of what the embossed timing marks say to compensate for the reverse rotation?

    Many thanks in advance!

  2. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Are you sure the engines rotates "the wrong way"?
    I have props rotating in opposite directions because one gearbox is in reverse, the other one in fwd. The engines rotate in the same direction.

    Letting an engine rotate reverse is not impossible but requires a special - so expensive - camshaft and lubrication pump.
  3. Jango
    Joined: Aug 2005
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    Jango Senior Enthusiast

    Yes, you should set timing in reverse for opposite rotation engines.
  4. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Some engines have the timing marks reversed. If not, use the TDC mark.and an adjustable timing light.

  5. 2850 Bounty
    Joined: Oct 2008
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    Location: Portland, Oregon

    2850 Bounty Junior Member

    JK, I am new to your forum.... however, I am not new to marine work and forum discussions.
    I do the Volvo Penta AQ series drives (primarily) and of course, with the V/P I/O's, there is no reverse rotation engine for twin engine applications.
    But I am familiar with some, and I'll offer a couple of additional points if I may.

    First.... yes, your harmonic balancer must be appropriately marked off and counter-clockwise of the Factory TDC mark in order to properly time this engine.
    You may even need to change the timing chain cover "tab" to compensate for the added degrees needed UNLESS the balancer is marked up to, and including, 30 degrees or so for TAT.

    Your ignition distributor is standard rotation, due to oil pump rotation, so adjustment direction here is the same.
    Time this as you would a LH engine.

    Remember..... not only do we set/check Base Timing ...... we need to set TAT as well.
    Whether Standard or Reverse rotation, your Total Advance Timing is equally important for a Marine Gasser. (follow your OEM specs to determine this setting)

    If this ignition is a "mechanically advancing system", I'd strongly encourage you to NOT use or depend on a digitally advancing type light...... and to use a good ole "strobe" type timing light .....
    You want Real Time, in Real Degrees when timing a marine engine and especially TAT........ IMO here.
    This is just too important!

    Thanks for letting me chime in!
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