Maintenance Log for Syzygy Sailing

two worrisome noises–transmission/prop shaft rotation

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we’re in mexico now and I have a few dozen posts to add and update on this site but I’m trying to get a tan and relax and unwind some from boat work. Anyway, on the way down from san francisco I listened to our transmission making a clacking noise which may or may not be completely normal.

The audio file I am attaching to this post was recorded while sailing (motor was not running), and the gear shift is in neutral. But it makes the same sounds regardless of whether the gear shift is in forward, neutral, or reverse (it doesn’t seem to make a difference).

You will hear the whirring of the prop shaft spinning, and then you will hear a clattering/clacking noise that I can pinpoint to be coming from the transmission (not the engine or v-drive).

Does anyone have any opinion about whether this is normal, or something I should be worried about?

Now, the second noise is one that I attempted to record, unsuccessfully. It is a deeper vibration that occurs in the prop shaft as we are surfing a bit faster than average. It happens regardless of whether we are motoring, or sailing and the prop is freewheeling. I watch the prop shaft and I see no untoward deflection or vibration, to my eye at least. I suspect the noise has something to do with the cutlass bearing; I do not know what shape the cutlass bearing is in. At what point do I need to worry?

SANY0236

update 11/11:

After sailing across the pacific without developing any problems associated with the noise, I have concluded that it is nothing to be concerned about.  We did make a modification to our procedure, however, which seemed to reduce the amount that the shaft spins: before shutting down the engine each time, we briefly put it in reverse and idle up slightly, for a few seconds, then turn off the engine without taking it out of gear. Honestly, I can’t ascertain the precise effect of this: sometimes the shaft still spins, sometimes not so much, but I don’t think I ever heard the noise again quite as bad as I described above.  In either case, no ill effect has come from it, despite about 15,000 miles of sailing.

Comments

6 responses to “two worrisome noises–transmission/prop shaft rotation”

  1. Siesta

    Hi Matt,

    Although I have the Perkins on Siesta (Thanks for looking at her in San Diego), i have a different setup on the transmission so I am not familiar with the v drive. I found a link that refers to a noise being caused by an alignment issue. I am not even sure if you have this model but thought I would give it a try. Hope this helps;

    CAUTION: Vibration, gear noise, loss of rpm and premature oil seal and bearing failure can be caused by misalignment of propeller shaft coupling and transmission output coupling flange.

    How to fix it: http://www.marinemechanic.com/site/page109.html

    Shawn and Karen

  2. Pete

    Have you dove on the prop? I know it sounds like the clanking is coming from the transmission, and maybe it is, but the character of the sound is more like sonething a fouled prop might generate. it seems possible to me that such a noise could be conducted along the prop shaft and transmitted to the transmission. another possibility is vibration from the prop as you surf down waves and a worn cutlass cause the prop shaft to vibrate and that vibration is causing parts in the transmission (perhaps the shaft against the bearing or a thrust washer) to hit together. This latter would indicate excessive wear in those areas since there shouldn’t be any play between shaft and said parts. to my ear, the sound is definitly more at the frequncy of a prop than anything inside the transmission.

    Id be curious to hear what you discover.

  3. Justin

    A bit off topic. I saw you used a flexible urethane casting compound like spatite.
    Now 2 years later would you use that again?

  4. admin

    yes; as far as I can tell it is identical to spartite

  5. Richard

    I clamped a vice grip on shaft between V-drive and stuffing box on multi day sails and hung a reminder sign on ignition key/button switch.

  6. Chaz

    Matt,
    The clanking sound may come from a worn damper plate. When under sail the prop shaft may spin freely, but the actual physical link to the engine flywheel may not be completely removed and so the prop shaft is exerting rotational force to the damper plate which, when worn can rattle. Another test may be when motoring through a rough sea, the propeller may rise above (or nearly enough so) the water and the lessened resistance will momentarily allow it to spin at a faster rate then the engine/transmission is expecting. This can cause the worn damper plate to rattle/clank until it ‘catches up’ and absorbs the shock. It looks like you have pretty cramped space in the engine room, but the replacement of the damper plate doesn’t need a ton of room, the transmission just has to be moved out of the way.

    Chaz

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