Shaft bearing temperatures

Discussion in 'Inboards' started by Commuter Boats, Jun 1, 2016.

  1. Commuter Boats
    Joined: Oct 2006
    Posts: 177
    Likes: 12, Points: 18, Legacy Rep: 182
    Location: Southeast Alaska

    Commuter Boats Commuter Boats

    Good morning folks, I've got some questions about shaft bearing temperatures.
    Shaft alignment is something that I don't normally get called for in less there's somethings unusual or somebody else has made a significant mess, two external cutlasses / struts on a twin-engine yacht, vessel lengthening, etc.
    I have a great client with a 40-year-old commercial fishing boat who undertakes a big job every other year on his vessel with the intent to rebuild better than new. A few years ago I was involved in replacing the stern bearing while another mechanic replaced shafting and realigned the engine/ shaft bearings. Last fall my client hauled out so that I could replace the little bulkhead that the shaft gland was mounted on, I chipped out concrete, renewed the shaft tube and replaced the bulkhead. Got everything hooked back up so the client could launch the boat and returned to his slip where I demoed most of the fishhold and shaft alley, built new support beams for the intermediate bearings and other associated work. Works completed and on sea trials the aft bearing was running at about 112° and the forward one was running at closer to 130°. I've mucked around with it some and presently have the aft bearing at 116° and the forward bearing at 112° when the boat is run hard ( temperatures are lower at normal cruise ). The gland is staying within a couple degrees of the ocean temperature with only a minimal amount of water passing the packing. The shafting is about 22 feet long, 2 inch stainless with about 5 feet between the transmission and the first bearing, 5 feet between the two bearings, and about 4 feet between the aft bearing and the cutlass with a shaft coupling close to the aft bearing. There's about 6 feet between the gland and the stern bearing.
    I'm not knowledgeable enough to know what the best case scenario might be as far as temperatures and how much effort I should put into improving the situation.
    Recommendations and past experience would be appreciated, thanks
    Gerald
    pictures to follow in another post :) b
     
  2. Commuter Boats
    Joined: Oct 2006
    Posts: 177
    Likes: 12, Points: 18, Legacy Rep: 182
    Location: Southeast Alaska

    Commuter Boats Commuter Boats

    Photos starting with the stern bearing replacement and ending with the completed project.
    P5130103.jpeg

    P5130110.jpeg

    P5130118.jpeg

    P5140004.jpeg

    P5170001.jpeg
     

    Attached Files:

  3. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 109, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    The last issue of Pro Boat Builder had a great article on shaft work with a lazer.

    Your bearing temps do not sound out of line as heat is also passed down the shaft from the engine .

    If its not shaking and making vibrations , What me worry?
     

  4. Commuter Boats
    Joined: Oct 2006
    Posts: 177
    Likes: 12, Points: 18, Legacy Rep: 182
    Location: Southeast Alaska

    Commuter Boats Commuter Boats

    Thank you Fred, I had scanned that article but didn't see anything about bearing temperatures. Through searches on bearings, some discussion on another forum and some old-fashioned calling mechanics on the telephone I've come to understand that my temperatures are acceptable.
    As too shaking and vibrations, this is a commercial fishing boat and my goal was to make it as quiet as possible.
    Thanks all.
    Gerald
     
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