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07-09-2019, 07:01
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#1
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Registered User
Join Date: Oct 2017
Location: MAINE
Boat: Cal 39 MKII
Posts: 54
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Do Most Yanmars Have a Vibration Range Harmonic
I have a 4JH4E on a Cal 39 MK2. The engine runs smoothly from idle to 1800 rpm then vibrates wickedly until about 2300 rpm then is reasonably smooth to about 2600 rpm. I have a two bladed Maxprop feathering prop.
I have wondered if this is "normal" for Yanmars (a fellow sailor with Yanmar has almost the same range vibration issue).
I would think that if this was a shaft or prop balance issue it would be constant throughout the RPM range.
The cutlass bearing is fine with no noticeable wobble.
Does anyone have any thoughts regarding this vibration issue as it pertains to either the natural harmonic of the boat / engine?
Thank you
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07-09-2019, 07:06
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#2
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Registered User
Join Date: Oct 2007
Location: Lakewood Ranch, FLORIDA
Boat: Alden 50, Sarasota, Florida
Posts: 3,470
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Re: Do Most Yanmars Have a Vibration Range Harmonic
Could be the shaft, bearing, prop or balance wheel but it’s definitely not normal.
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07-09-2019, 08:00
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#3
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Moderator
Join Date: Mar 2009
Location: Denmark (Winter), Helsinki (Summer); Cruising the Baltic Sea this year!
Boat: Cutter-Rigged Moody 54
Posts: 33,865
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Re: Do Most Yanmars Have a Vibration Range Harmonic
My Yanmar has no such thing.
I suspect this is not in the engine, but downstream of there.
I've had some vibration in previous years, which was cleared up with a new cutless bearing. Alignment is also important; as are motor mounts, and prop balance. Here you need a good engineer, and it's NOT normal -- fix it.
__________________
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I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
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Cushion me soft . . . . rock me in billowy drowse,
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07-09-2019, 08:02
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#4
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Registered User
Join Date: Aug 2019
Posts: 90
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Re: Do Most Yanmars Have a Vibration Range Harmonic
Quote:
Originally Posted by epoxyman
I would think that if this was a shaft or prop balance issue it would be constant throughout the RPM range.
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That wouldn't be the case because different rpms create different harmonics. A property known as 'resonant frequency' is inherent in all components and just as waves can build upon each other, or cancel each other out, the same can be said of your drive system.
If your Yanmars have no vibration at those rpms when the shaft is not spinning, (tranny in neutral) and occur only when the shaft is turning than you need to look at the shaft system, that being the shaft, bearings, couplers, prop, zincs, etc.
As silly as it sounds changing the shaft zinc may be all that is required to change the harmonics and get rid of the vibration in a best case scenario.
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07-09-2019, 08:49
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#5
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Registered User
Join Date: Mar 2016
Boat: Lagoon 440
Posts: 736
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Re: Do Most Yanmars Have a Vibration Range Harmonic
Quote:
Originally Posted by epoxyman
I have a 4JH4E
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I have two on my cat, one use to vibrate as you describe, I changed the mounts last winter and the vibration magically disappeared ...
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07-09-2019, 08:51
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#6
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Registered User
Join Date: May 2013
Location: Morro Bay, CA
Boat: Herreshoff 28 modified ketch- wood
Posts: 379
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Re: Do Most Yanmars Have a Vibration Range Harmonic
I had vibration in my Yanmar 2gm20. I put an old two blade prop that came with the boat and replaced the three year old Acme 3 blade prop. Very smooth, no vibration at any speed.
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07-09-2019, 09:01
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#7
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Registered User
Join Date: Feb 2015
Location: St. Petersburg, FL
Boat: Beneteau 411
Posts: 14
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Re: Do Most Yanmars Have a Vibration Range Harmonic
If the vibration happens at a specific frequency range, it is a resonance issue. Resonance is a function of the mass that's vibrating and the stiffness of the mounting spring. In this case the mass (engine) is what it is. The spring is the mounts which are normally stiff enough so that the resonance frequency is much higher than your operating range. I would check your mounts.
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07-09-2019, 09:05
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#8
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Registered User
Join Date: Feb 2019
Location: Point Richmond, CA
Boat: Hunter 46
Posts: 777
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Re: Do Most Yanmars Have a Vibration Range Harmonic
To answer your question no.
During the sea trial of our new to us Hunter 46 we experienced a similar vibration from our Yanmar. During haul out for an out of water survey discovered one of the 3 propeller blades had holes in it caused by corrosion. Replaced the 3 bladed propeller and the vibration went away.
Similar issue occured on my Spindrift Motor yacht with two Volvo Penta engines during its first trip up the coast from Los Angeles. Apparently one of motors was not aligned properly after new shafts were installed. After arriving in San Francisco the engine motor mounts were adjusted and the vibration want away.
Similar thing occurred on my waterski boat with a PMC marine engine. When I pulled the boat out of the water discovered a piece of submerged wood lodged itself on a fin ahead of the propeller which caused water to vortex around the propeller. Once I removed the wood the vibration went away.
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07-09-2019, 11:08
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#9
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Registered User
Join Date: Jun 2014
Location: Hampton, Va
Boat: Freedom 32'
Posts: 531
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Re: Do Most Yanmars Have a Vibration Range Harmonic
My Yanmar 3YM30 has no vibration and I also have a Max 2 blade feathering prop.
__________________
Life shrinks and expands in proportion to one's courage.
Anais Nin
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07-09-2019, 11:20
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#10
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Do Most Yanmars Have a Vibration Range Harmonic
Quote:
Originally Posted by Shenandoah52
That wouldn't be the case because different rpms create different harmonics. A property known as 'resonant frequency' is inherent in all components and just as waves can build upon each other, or cancel each other out, the same can be said of your drive system.
If your Yanmars have no vibration at those rpms when the shaft is not spinning, (tranny in neutral) and occur only when the shaft is turning than you need to look at the shaft system, that being the shaft, bearings, couplers, prop, zincs, etc.
As silly as it sounds changing the shaft zinc may be all that is required to change the harmonics and get rid of the vibration in a best case scenario.
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This, trust me from a 20 yr experience of maintaining helicopters. It the SYSTEM, not the individual parts that exhibit harmonic resonances, and identical aircraft due to slight differences can exhibit different harmonics, many things were done to discourage harmonics like odd gear ratios, components spinning at different RPM’s etc. , but it still was occasionally an issue.
Even if the engine doesn’t vibrate at X RPM or the drive train, it’s entirely possible that the two of them do, but don’t separately.
It’s common for example for an airplane that had a two blade prop for extended time to have a harmonic if a three blade prop is fitted, where it wouldn’t if it was fitted from new, but no one, or none that I could find in Hartzell propellor or Avia Propellor or Lycoming engine’s could explain either why or how, but Engineers from all three recognize the issue.
Sometimes the Science breaks down and you solve it by trial and error, or give up trying.
Really, honestly once you determine there is no fault like bad motor mounts and or shaft alignment etc, about all you can do is transition though ranges that exhibit harmonic resonance, do not operate in them. Excessive wear can and will result.
On edit it could be a bad / dirty injector causing what amount to a misfire. You just have to start eliminating things, and if you don’t know when the injector were last cleaned they likely could use it anyhow.
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07-09-2019, 11:21
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#11
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CLOD
Join Date: Jul 2007
Location: being planted in Jacksonville Fl
Boat: none
Posts: 20,415
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Re: Do Most Yanmars Have a Vibration Range Harmonic
Quote:
Originally Posted by epoxyman
I have a 4JH4E on a Cal 39 MK2. The engine runs smoothly from idle to 1800 rpm then vibrates wickedly until about 2300 rpm then is reasonably smooth to about 2600 rpm. I have a two bladed Maxprop feathering prop.
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i have same engine with 3 blade FOF, it doesn't vibrate
__________________
Don't ask a bunch of unknown forum people if it is OK to do something on YOUR boat. It is your boat, do what you want!
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07-09-2019, 11:27
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#12
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Do Most Yanmars Have a Vibration Range Harmonic
Harmonic resonance, in this case it’s called ground resonance, but shows how destructive resonance can be.
https://youtu.be/0FeXjhUEXlc
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07-09-2019, 11:42
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#13
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Registered User
Join Date: Aug 2019
Posts: 90
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Re: Do Most Yanmars Have a Vibration Range Harmonic
Quote:
Originally Posted by a64pilot
Even if the engine doesn’t vibrate at X RPM or the drive train, it’s entirely possible that the two of them do, but don’t separately.
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Yes, what you said is indeed true. I alluded to that same phenom when I said, "A property known as 'resonant frequency' is inherent in all components and just as waves can build upon each other, or cancel each other out, the same can be said of your drive system."
And when I said, "If your Yanmars have no vibration at those rpms when the shaft is not spinning, (tranny in neutral) and occur only when the shaft is turning than you need to look at the shaft system,..." I was also alluding to the same phenom as your example where the engine ran fine until coupled to another component such as the props you mentioned. My suggestion being to look at the shaft system first.
We're basically on the same page here but I think you gave a good explanation that was probably better than mine.
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07-09-2019, 12:30
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#14
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Registered User
Join Date: Mar 2012
Location: San Diego Ca
Boat: Hunter, 420 Passage
Posts: 64
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Re: Do Most Yanmars Have a Vibration Range Harmonic
I have 4jh3e , Had a bent shaft and broken motor mount ,Didn't know it ,Increased rpm 500.
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07-09-2019, 12:35
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#15
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Registered User
Join Date: Sep 2012
Location: West Chester, PA
Boat: Beneteau 48
Posts: 30
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Re: Do Most Yanmars Have a Vibration Range Harmonic
We have had two boats with 4JH4TE engines. 730 hours on this one (saildrive)
We have never experienced a vibration. You don’t have an engine issue, look elsewhere as others have suggested: engine mounts, cutlass bearing, prop, zinc.
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