Tuesday, October 25, 2011

Wits End

Fernandina Beach, Florida
30 43.14 N 081 32.78 W

We're at the City Marina a few days.  My friend Charlie connected me with a mechanic.  He ordered new mounts.  We'll put them in Thursday.  

Jeff and Wendy commented on my problems.
Your temporary repair to your engine was very ingenious, I'll have to remember it. Unfortunately, it sounds like the problem you had with a broken motor mount may just be a symptom. When you mix it with the shaft seal leaking issue it may be a growing problem with your engine or possible its alignment.
I certainly agree with them.  But I'm at wits end.   We had the new motor re-aligned twice already.  I had the shaft straightened and checked and the propeller balanced.  I've spent $3000 so far trying to cure the problem with no results.  Still, the motor shakes.  Evidently, it shakes so much that it ruins motor mounts in just 2 years.  The previous Perkins 108 motor shook just as much, so I've come to accept it as normal.   My problem is that I have no experience with an inboard diesel that didn't shake.  I don't know what level of vibrations are normal.

I have two more clues.  My transmission ratio is 2:1.  According to Beta, all other W32s with Beta engines have a 2.5:1 ratio.  I, and they, have no idea why mine came different.   A second clue, if we run at more than 2000 RPM, the engine temperature begins to climb.  My top RPM at full throttle is 2500.  Some people say I should have the prop pitch set for 3000 RPM tops and cruise at 2400.   But if I did that, the vibration and the temperature are both too high.  Could it be the transmission ratio?

A third possible clue.  We use a shaft saver coupling between the transmission and the shaft.  I replace that also, the last time we changed the mounts.  To align the engine, they must remove the shaft saver, align, then replace the shaft saver.  Could having a shaft saver in the first place spoil the alignment?  It's not easy to remove it.  Without the shaft saver, the shaft is too short.  I would have to have a new shaft made to test it.

I'm at my wits end what to do next.  When these mounts are replaced the alignment must be re-done, but for how long will it last?  I wonder if I shouldn't take another approach.  Find a mechanic to take the job on a results-oriented basis.   "Fix my vibration problem.  Whatever it takes.  I don' pay a cent until it runs smooth as silk."   I worry that they'll charge me more than the cost of a new engine to accept that risk.  What do you think?

4 comments:

  1. I think I would try to eliminate any sort of shaft savers or etc., and just go for "perfect" alignment in the most basic sense, with no extras.

    Things I would check:

    1) Are the engine beds secure and immovable.

    2) Is it possible to perfectly align the engine with the stern tube? (sometimes there are "built in" problems with a stern tube that make that impossible without changing something).

    3) Is the stern tube immovable or is it somehow able to shift?

    I think I would start with those basics. IF the stern tube needs changing, and a new one is needed, I would glass in a fiberglass tube, situating it so you CAN get good alignment. It's not that hard, and good tubes can be had pre-made.

    I would get a new shaft (recommend bronze or aquamet 22) that is long enough to use without any "savers"

    Then once things were aligned, I would find out what the engine mfgr's recommended attainable WOT rpm's were, and make sure I could attain that. If not, then change prop to make that possible.

    Just some input from a fellow sailor.

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  2. Dick,
    I have the same setup you describe: Beta 37.5 engine, shaft saver etc., installed by Bud Taplin with his special Beta motor mounts. He also put in a replacement cutless (or cutlass) bearing connected to a new stuffing box. Have you replaced the cutless bearing? Is it possible that the bearing is misaligned?
    Doug

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  3. Dick - I can't add much other than the observation that I'm running a Beta 28 on my Bristol 35.5 and I have the shaft saver. I've only got 250~ hours on the engine but we have almost zero vibration, so much so that friends find it hard to believe how vibration free she runs - Are your motor mounts the style with the hard rubber bushings/feet? Stan at Beta Marine, just up from Oriental NC is a wealth of knowledge about his products and might be worth a call if you have not done so - (252) 249-2473 11702 Hwy 306 S, Minnesott Beach, NC 28510

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  4. Dick please take a movie of your engine shaking and post on youtube for us to see -- different RPM etc.

    I run my Beta 1505 engine at 2K RPM for 5.8 knots on a calm day with very little vibration and even less since the new cutless and shaft log installation.

    I'd also get Stanley involved -- maybe if you are close he can come to the boat?

    Jay

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