stern drive noise levels

Discussion in 'Sterndrives' started by Boa-Tr, Feb 13, 2014.

  1. Boa-Tr
    Joined: Jan 2010
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    Boa-Tr Junior Member

    Hi all,

    Is it possible if you can share your experience on stern drive deisel engines for noise levels. How irritating would it be on noise issue, while driving without exhaust inline muffler on stern drive deisel power boats. Eventually there should be waterlock on the exhaust exit, but I would like to hear if you have any bad experience on this.
     
  2. powerabout
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    powerabout Senior Member

    the exhaust elbow(s) are the high point so no water lock needed
    sterndrives do a good job of silencing
     
  3. CDK
    Joined: Aug 2007
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    CDK retired engineer

    The exhaust contributes only a little bit to the noise issue.
    Because stern drive engines are attached to the transom assembly, a lot of mechanical noise is conducted to the hull.
     
  4. Westfield 11
    Joined: Apr 2008
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    Westfield 11 Senior Member

    The exhaust contributes immensely to the noise of a sterndrive if routed through the transom with no muffling device. If you doubt me pull off the muffler of a diesel truck and see if it gets louder...... My Daycruiser has a wet exhaust through the transom just below waterline at rest and it will deafen you after a day on the water. We went to a muffler system and it helped a lot.

    Sterndrive engines are NOT attached to the transom. They are attached to the stringers in the hull, the drive assembly is attached to the transom and the engine is attached to the drive.
     
  5. gonzo
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    gonzo Senior Member

    Sterndrive engines are attached to the transom through the transom shield and have two forward mounts. Sterndrives are designed to route the exhaust and act as a wet muffler.
     
  6. Westfield 11
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    Westfield 11 Senior Member

    Just as I said, the engine attaches to the stringers (2 forward mounts) and to the sterndrive (transom shield) the drive then attaches to the transom. High performance sterndrives are not designed with through the prop hub exhaust, google Speedmaster drives to see. Low performance drives use this type of exhaust, but anyone serious about going over 80 or 90 mph has through transom pipes with no inline mufflers, heck, my old boat only goes 70 or so and I don't use the prop exhaust...... It chokes the engine.
     
  7. gonzo
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    gonzo Senior Member

    Westfield you had just said that "sterndrive engines are NOT attached to the transom". The emphasis was on "NOT". Which one is it? Besides I doubt the OP is referring to high performance engines. He is asking about a diesel installation.
     
  8. BMcF
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    BMcF Senior Member

    Several of the local commercial waterman run the Volvo diesel inboard-outboard drive (duo-prop, most of them) and they are certainly MUCH quieter than the other boats running straight prop drives and wet exhaust through the transom.
     
  9. Westfield 11
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    Westfield 11 Senior Member

    The sterndrive attaches to the transom. The engine attaches to the stringers and to the sterndrive. Yes the engine is eventually connected to the transom via the drive, but not directly. In fact on my boat, there is a Borg-Warner marine gearbox between the sterndrive and the engine. By your logic, I suspose you could say that the cylinder heads are attached to the transom too since they are attached to the engine and the engine is attached to the gearbox and the gearbox is connected to the sterndrive and the drive is attached to the transom. Where do you stop, is the anchor windlass also attached to the transom too?
     
  10. gonzo
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    gonzo Senior Member

    There is a transom shield that has on the outside a gimbal/pivot where the sterndrive gets attached to. On the inside, it has two mounts for the rear of the engine and a bracket for the steering. I would stop at the rear engine mounts.
     

  11. powerabout
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    powerabout Senior Member

    unless its the forward engine on a staggered rig..then 4 mounts on the stringers
     
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