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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 05-26-2004
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lgsailor19 is on a distinguished road
Vibration dilemma

On my Catalina 30, with Universal 25, we get a vibration at various rpm''s. Sounds like something loose rattling in the locker, but we cannot locate anything. We replaced the prop, the cutlass bearing, checked engine alignment, made sure the zinc was on fast. The vibration is more apparent at certain rpm''s , but seems to dissapear at others. No rattle with the transmission in neutral at any rpm. Any ideas??
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Old 05-26-2004
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GordMay is on a distinguished road
Vibration dilemma

No vibration in neutral suggests drive train.
You seem to have checked it out pretty thoroughly, but didn''t mention the shaft to transmission coupling, strut, nor shaft straightness.
Sounds like a "puzzle", all right.
Gord
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Old 05-26-2004
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DuaneIsing is on a distinguished road
Vibration dilemma

lgsailor19,

If you have one of those dripless shaft seals, I know they can vibrate under certain conditions.

If you have one and wish to check it, you can VERY carefully observe it while the transmission is engaged (nothing dangling near roating machinery). In the case I observed, carefully applying pressure to the rubber bellows changed the face seal contact ever so slightly and stopped the vibration (which was surprisingly loud).

To be frank, I don''t know what the long-term solution is in that case, but at least you would know.

If you don''t have a dripless shaft seal, then I take my cue from Saturday Night Live''s Roseanne Rosanadana, "Never Mind!"

Good luck.
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Old 05-26-2004
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andiamod11 is on a distinguished road
Vibration dilemma

You might want to check the shaft strut to make sure it has not loosened up. Other problems could be a bent shaft or insufficient propeller tip clearance with the hull.
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Old 05-27-2004
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Yodagwb is on a distinguished road
Vibration dilemma

Many boats with diesels have RPMs which the boat is not happy with. I have a range in my Cat350 which make all kinds of things rattle and weird sounds, harmonic resonance. Once you get away from that RPM range things quite down. Could this be what you are dealing with?
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Old 05-31-2004
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lgsailor19 is on a distinguished road
Vibration dilemma

The vibration is too loud to be harmonic resonance. My yard mechanic tells me it is a livable situation, that it is no worse than most boats. The vibration has been with me only the last 2 seasons. Prior to last season, no vibrations. Any other ideas? Help!
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Old 05-31-2004
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garygroves is on a distinguished road
Vibration dilemma

You might check your engine mounts to see if one may have a break or worn rubber. While you say you don''t have any vibrations when xmsn is not engaged, typically a broken engine mount would show up here as well. However, the break may be small, such that it needs the additional torque of the spinning shaft to start the vibration sequence. Just a thought to go along with the rest.
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Old 06-03-2004
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lgsailor19 is on a distinguished road
Vibration dilemma

How can the driveshaft straightness be checked, short of hauling out and removing the shaft itself?
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Old 06-04-2004
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capnjim02 is on a distinguished road
Vibration dilemma

I think there may possibly one other culprit. Its possible that your injectors or possibly one of them may be fouled. under load it may not be correct and causing the engine to miss under load. happened to my friends volvo. one injector was not spraying correct pattern. had it rebuilt and vibration went away.
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Old 06-08-2004
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lgsailor19 is on a distinguished road
Vibration dilemma

It isn''t engine related. I think my best leads are; slightly loose strut or a bent prop shaft.
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