Inboard shaft question....

Discussion in 'Boatbuilding' started by Hypercat, Sep 24, 2004.

  1. Hypercat
    Joined: Apr 2004
    Posts: 10
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    Location: New Jersey

    Hypercat Junior Member

    On boats with inboard engines, where is the thrust produced by the prop directed to? The gearbox? a thrustbearing located somewhere on the shaft? the stern bearing? Excuse my ignorance but I cant find an example of one anywhere. I'm refering to smaller 15-25 ft ski boats & not I/O's Thanks.
  2. Eric Sponberg
    Joined: Dec 2001
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    Location: On board Corroboree

    Eric Sponberg Senior Member

    Without any thrust bearings, the thrust from the propeller shaft goes directly into the gearbox, the engine, and the engine mounts, then to the hull structure. With a thrust bearing, the bearing is hardmounted into the boat between the stern tube and the gearbox. All the load then goes to the thrust bearing and the boat structure. There is then no thrust load between the thrust bearing and the gearbox/engine. Therefore, with a thrust bearing, the engine and gearbox can be mounted on softer mounts, thereby reducing structure-borne vibration.

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