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Old 01-19-2017, 06:38 PM   #1
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OA 64 & it's MTU 825 hp Engines

A very good friend of mine is getting quite a pronounced vibration in his starboard engine. When in neutral, it runs like a sewing machine, without a hint of vibration. in gear, the vibration starts again. The engines were just re-aligned (they were way out of alignment) & the props pulled and tuned in an effort to pin down the problem. He ran the boat today and the vibration is still there. We think the next step is to haul the boat, check the cutlass bearings for slop and check the shaft with a dial indicator. When i use the word vibration, it's really more like "boom. boom. boom.)

Does the Forum have any ideas?
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Old 01-19-2017, 07:59 PM   #2
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one thing to check is the frequency of the vibration, and you can do that with some smart phone apps. If the frequency is there out of gear (neutral) then it's an engine issue. If it is a problem in gear, see if it follows as the engine revs up.

From what you said in your report, everything but the shaft has been balanced...

That could be a source.

Are the shafts long in that boat, and if so, are they supported by pillow blocks inboard and struts outboard?

Lots of things to check...
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Old 01-19-2017, 08:23 PM   #3
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Walt,
"The engines were just aligned"
Sounds like somebody made a big mistake.
Something still loose?
Rubber part of a mount torn open and perhaps not obvious.
Something like that is possible.
Only on one engine eh?
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Old 02-14-2017, 05:54 PM   #4
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Walt,
"The engines were just aligned"
Sounds like somebody made a big mistake.
Something still loose?
Rubber part of a mount torn open and perhaps not obvious.
Something like that is possible.
Only on one engine eh?
Eric, Sorry for the very tardy response! We are pulling the boat on 2/21 and are planning on dial indicating the shafts (pulling them if necessary) Checking the props (also pulling them) checking the cutlass bearings, etc. The boat will be laid up in the yard until a solution is found and the fault(s) corrected. It aint going to be cheap!
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Old 02-14-2017, 06:56 PM   #5
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If the vibration is present in idle in neutral, then it's not an alignment issue. Sounds more like some sort of uneven firing between cylinders. Maybe an injector over or under fueling a cylinder, or some such thing.
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Old 02-14-2017, 06:57 PM   #6
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If the vibration is present in idle in neutral, then it's not an alignment issue. Sounds more like some sort of uneven firing between cylinders. Maybe an injector over or under fueling a cylinder, or some such thing.
Oh, unless the vibration damper is coming apart? That might be worth checking.
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Old 02-14-2017, 07:15 PM   #7
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Greetings,
Mr. tt. I think Mr. C2 stated in his opening remarks that it was smooth at idle and the vibration developed when in gear ...
No, make that boom, boom, boom...



Sorry, it was either that or Peter Gabriel...
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Old 02-14-2017, 07:40 PM   #8
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Best to troubleshoot it before it goes on the hill. Could be misfire, shaft runout, crappy couplings, bad prop, bad mounts, cosmic gremlins, hypocondriac owner, etc.

Crappy alignment rarely causes vibes.

Easier to sort if techs doing the troubleshooting get to go for a run and observe.
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Old 02-14-2017, 09:50 PM   #9
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The first place I would look for a "boom, boom, boom" noise would be the gearbox.
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Old 02-15-2017, 01:16 AM   #10
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Greetings,
Mr. tt. I think Mr. C2 stated in his opening remarks that it was smooth at idle and the vibration developed when in gear ...
No, make that boom, boom, boom....

Thanks. I miss-read his original post.
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Old 02-15-2017, 02:58 AM   #11
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You can read this


check the vibration damper
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Old 02-15-2017, 05:02 AM   #12
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other possible cause of a steady blast of:
-crankshaft bearing damage
-cranksaft crack
-valve does not move, carbonized or bad measures or the valve plate is crack and top of the piston
-the sprayer nozzle damage, may cause noise
-the timing ted tooth is broken or a wedge.
-the feed pump drive coupling broken
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Old 03-26-2017, 01:38 PM   #13
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To sum up: The boat was pulled, starboard prop had a large dent in it, (Diver should have noticed that.) both props were sent out and machined, shafts were pulled and checked for warp, cutlass bearings were replaced and when the boat was splashed, engines were re-aligned.

Result: Boat ran like a Swiss watch, vibration free all the way up to 21 knots.
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Old 03-26-2017, 01:54 PM   #14
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To sum up: The boat was pulled, starboard prop had a large dent in it, (Diver should have noticed that.) both props were sent out and machined, shafts were pulled and checked for warp, cutlass bearings were replaced and when the boat was splashed, engines were re-aligned.

Result: Boat ran like a Swiss watch, vibration free all the way up to 21 knots.
" the props pulled and tuned in an effort to pin down the problem."

So how did the prop get a large dent in it if the props were just reworked?
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Old 03-26-2017, 02:09 PM   #15
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So how did the prop get a large dent in it if the props were just reworked?
That's the $64K question! During lobster season there are traps all over the channel. It reminds me of the stories coming out of Maine. The owner thinks he hit a trap but is not sure. At any rate the problem is fixed and the owner is ecstatic!
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Old 03-26-2017, 02:38 PM   #16
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Good to hear. A much simpler fix than some other issues. It's good that he replaced cutlass bearings.
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