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Old 14-09-2019, 15:24   #31
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Re: Do Most Yanmars Have a Vibration Range Harmonic

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Originally Posted by a64pilot View Post


My engine mounts were about 29 yrs old when I changed them and gave no problem, and seemed fine, so I believe they will last longer than four years myself. Iím pretty sure they were original as they had the Yanmar grey paint on them and new mounts donít come painted.
I need to get around to changing those 32 yr old hoses on the engine.
Re yr 32 year old hoses if that includes fuel hose can tell you that I had trouble with a 36 year old fuel hose on our Yanmar & when I removed it it crumbled in my hand. The engine kept slowing down which alerted me to the problem.
Yanmar wanted $130 for a hose with crimped ends that went maybe 5" from filter bowl to lift pump. I just laughed & hung up the phone. Cut the crimped ends off the old banjo fittings & reused them with double ss hose clamps on generic fuel line.
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Old 14-09-2019, 17:12   #32
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Re: Do Most Yanmars Have a Vibration Range Harmonic

Itís the water hoses that are that old, just the water ones I think. I replaced the one to the raw water pump myself. Boat is 32 yrs old and the water hoses are painted, which makes me think they are original.
I have silicone hoses to replace them all, at least the raw water side, just need to get a round tuit.
Iím also plumbing in a strainer just after the raw water pump too. About ready to get started.
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Old 16-09-2019, 06:32   #33
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Re: Do Most Yanmars Have a Vibration Range Harmonic

On our boat we had vibration as mentioned. We had the shaft and prop checked and aligned along with an engine alignment. That solved our problem. But, getting the alignment just right took some work.

Cheers, RickG
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Old 16-09-2019, 09:36   #34
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Re: Do Most Yanmars Have a Vibration Range Harmonic

Cutlass bearings can be worn way before a visible wobble develops.
I replaced them on a pair of Hamilton Jet drives and the difference was dramatic. The mechanics said they were fine. I said change them out they are relatively cheap. well worth it.
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Old 16-09-2019, 10:37   #35
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Re: Do Most Yanmars Have a Vibration Range Harmonic

I have a Yanmar 3GM30f. It idles at about 600, and when increasing the speed slowly, at about 800 it will shake itself to death. The manual mentions this characteristic and warns to avoid that RPM. So it does have some balance issue that appears only at that speed.
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Old 17-09-2019, 09:02   #36
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Re: Do Most Yanmars Have a Vibration Range Harmonic

In a land far away in a remote time portal I was a marine mechanic and electrician... small to larger yacht engines and other applications. Mostly diesel

Check the issue for sources one at a time. The advice on the forum from contributors is very good.

I tackle problems like this by the $ numbers and by which is easy to check.
Motor mounts, missing bolts etc... corroded bolts and dry rot in stringers. All of these can and do happen.

Rule these out. Then get to the deeper and more difficult items one at a time.
Many Yanmars came with very soft engine mounts.

I suspect that A64 hit the hammer with his head and mentioned your exact solution. Maintaining Helicopters requires a high degree of skill, training, and experience. I pay attention to what these people say. I am alive. Thanks to the team.

Good post as it is a frequent experience for boaters.

When multiple engines are involved, the engines may sing happily together, hum a continuity, or dance to a devilish rhythm. When they are right, it is musical beauty and a delight like good Mozart.

When an engine is 'off' it is abrasive to the heart and can ruin a voyage until the repair is successful. Not a nice way to stay awake listening to the throb in the dark... painful. Like a lot of poor poetry or angry hip hop. Turn the engine off and sail!

Cheers
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Old 18-09-2019, 16:29   #37
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Re: Do Most Yanmars Have a Vibration Range Harmonic

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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


Yanmar have made an interesting new 50hp two cylinder diesel outboard. Like the old 4JHY it has two two contra rotating balancers but now uses two crankshafts rather than dedicated gear driven balancers .....and two conrods on each piston. It's alleged that this engine is amazingly vibration free but I'd like to see that myself before deciding on Yanmar's claims.
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Old 18-09-2019, 16:45   #38
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Re: Do Most Yanmars Have a Vibration Range Harmonic

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Yanmar have made an interesting new 50hp two cylinder diesel outboard. Like the old 4JHY it has two two contra rotating balancers but now uses two crankshafts rather than dedicated gear driven balancers .....and two conrods on each piston. It's alleged that this engine is amazingly vibration free but I'd like to see that myself before deciding on Yanmar's claims.
Wow 2 conrods per piston. The yanmar agent will be hoping for major engine repairs on one of those!
Mite fund his space tourism jaunt
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Old 19-09-2019, 00:37   #39
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Re: Do Most Yanmars Have a Vibration Range Harmonic

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Wow 2 conrods per piston. The yanmar agent will be hoping for major engine repairs on one of those!

Mite fund his space tourism jaunt


Yes , the times are a changing and not really for the better. The next new thing after the fiasco that is common rail injection with EGR is no camshaft, the valves are operated by cpu controlled solenoids and engine oil pressure, Konnigsegg have developed it and its coming soon to a boat near you...... try and fix that while on your way to Chagos!
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Old 19-09-2019, 01:05   #40
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Re: Do Most Yanmars Have a Vibration Range Harmonic

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I have the 4JH4-TE, it had 672 hours when we purchased the boat. And itnhad a vibration similar to what you mention.

I have:
Replaced the shaft
Replaced the prop with new
Installed a prop saver coupling
Had the engine aligned

Nothing made a significant difference.

In my case I think it is because we have a 7’ long 1-1/4” shaft. It is supported near the prop and then about 2’ behind the engine. So almost 5’ unsupported.

I think that distance is a bit much. My guess.

We generally run 1,700-1,800 RPM with the suggested bursts higher, although I didn’t do that at first. I’ve never seen any carbon build up. We now have about 2,200 hours in the engine.

Our Taswell 49 has a 1.5 inch monel shaft, otherwise configured like yours with about 5 ft unsupported. Only connected to boat at the outside strut and at the transmission flange. Our 4JH2-HTE (2900 hrs) is as smooth as glass in gear or out, any RPM. That point 2ft behind the engine you mention is a shaft log seal, not really a shaft support. A friend of mind thought once that I was in neutral when it wasn't, and agreed it was kind of hard to believe. I could never get our previous Ericson 38 with Universal Model 40 (4 cyl Kubota) to be this smooth in gear, so I think it is a matter of mass, rigidity, and resonant frequency.

The Taswell also has a flex coupling, and the max prop was recently rebuilt, but the engine mounts are original. Maybe since the boat is 40K pounds and the engine stringers are very deep (10 inches) and long, with steel bars buried inside them that the mounts screw into provides a stable non-resonant platform.
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Old 01-10-2019, 16:02   #41
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Re: Do Most Yanmars Have a Vibration Range Harmonic

Gents,
Here is the epilogue of sorts-
Yard manager and engine guy came with me on a sea trial and the engine guy dropped down into the sail locker to feel the rotating shaft and found that it was rubbing on the log.
It appears the aft engine mount blocks were not tall enough so the mounts were screwed all the way up and the shaft was still not centered in the log.
The engine guy has jacked up the engine, is installing new blocks and will re-center the shaft. While he is at it, I am having him service the PSS seal and the engine injectors. Should be good to go come spring - just a few boat bucks poorer.
Thank you all for your insight and suggestions
Epoxyman signing off
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Old 01-10-2019, 16:12   #42
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Re: Do Most Yanmars Have a Vibration Range Harmonic

Have the same engine...... smooth with no vibration.
As was said ..... down stream of engine.
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Old 01-10-2019, 16:57   #43
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Re: Do Most Yanmars Have a Vibration Range Harmonic

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Originally Posted by epoxyman View Post
Gents,
Here is the epilogue of sorts-
Yard manager and engine guy came with me on a sea trial and the engine guy dropped down into the sail locker to feel the rotating shaft and found that it was rubbing on the log.
It appears the aft engine mount blocks were not tall enough so the mounts were screwed all the way up and the shaft was still not centered in the log.
The engine guy has jacked up the engine, is installing new blocks and will re-center the shaft. While he is at it, I am having him service the PSS seal and the engine injectors. Should be good to go come spring - just a few boat bucks poorer.
Thank you all for your insight and suggestions
Epoxyman signing off

Make sure you let us know how it turned out next spring.
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Old 02-10-2019, 06:06   #44
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Re: Do Most Yanmars Have a Vibration Range Harmonic

Quote:
Originally Posted by epoxyman View Post
Gents,
Here is the epilogue of sorts-
Yard manager and engine guy came with me on a sea trial and the engine guy dropped down into the sail locker to feel the rotating shaft and found that it was rubbing on the log.
It appears the aft engine mount blocks were not tall enough so the mounts were screwed all the way up and the shaft was still not centered in the log.
The engine guy has jacked up the engine, is installing new blocks and will re-center the shaft. While he is at it, I am having him service the PSS seal and the engine injectors. Should be good to go come spring - just a few boat bucks poorer.
Thank you all for your insight and suggestions
Epoxyman signing off
Sounds familiar. The Volvo Penta D2-55A in our Beneteau 423 is very sensitive to engine alignment. Our engine is angled back enough that we have reduce the oil capacity a bit. We had the engine mounts replaced and the forward mounts raised so that the forward mounts were not at the absolute limit. It helped, but it is still sensitive to alignment.

Cheers, RickG
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