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Old 16-06-2016, 11:36   #31
F10
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Boat: S&S 34
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Re: Vibration troubleshooting help

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Originally Posted by AFKASAP View Post
Thanks. The mechanic did a visual inspection of the mounts and said they looked fine. How does one know for sure? I did call the Yanmar dealer that did the last service and they said the mounts should last many years (much more than they are old). They are from 2008 with about 900 hours on them.

One other thing. If they had started to sag I would expect the gap to be at the top of the shaft and not the bottom like it is. It appears that the engine should be lowered to correct the angle.

Beneteau Oceanis 40 - 2008
Mallorca
Engine mounts can fail in several ways. The rubber can break loose from the metal- to test need to try to lift engine some and see if mount rises up, or see if the mount has failed and metal separates from the rubber. if the mounts are sagging down and do not look like a pic of a new mount, then they might be worn out. If they are just sagging a small amount, may be able to use the mount adjustment nuts to raise and realign the engine.

My engine mounts were very rusted and when I lifted the engine, 3 of the 4 mounts had the rubber lift off the metal part of the mount. Basically only one mount was holding the engine in place and the other three the engine was just resting on the mounts.

I imagine you mounts are probably ok based on your description and their age.
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Old 16-06-2016, 13:42   #32
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Re: Vibration troubleshooting help

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Originally Posted by Cheechako View Post
The shaft will not become loose when you unbolt the coupling. It is very true that , although you may be out of alignment, it isn't necessarily the vibration problem. My 47 footer had a Nanni/Mercedes engine that at about 1500 rpm had a harsh vibration throughout the boat. It was not an alignment, bearing or motor mount problem. Nature of the beast I guess. I just avoided that rpm, but you have to pass through it going up and down.
Your problem sounds like a new one though, and hopefully it is that alignment.

Same thing with my boat. Alignment is perfect.
Smooth until 2200-2600 where it's unbearable. Of course, that's exactly the range in which I usually wish to motor.
The stern mounted barbecue rattles so much it seems to threaten to jump overboard.
Above that RPM range, smmoooooth again.
I used my Fluke ScopeMeter and an old speaker as a microphone just above the prop in the stern compartment deck. I measured the frequency of the vibration and proved it was resonance of ihull because the vibrarion was 2x the propshaft rpm which I measured by the tachometer divided by the transmission ratio. The 2x is because it's a two blade folding prop.

A friend suggested pouring concrete into a hole drilled in the aft deck.
Yeah right ! Concrete in the stern of a multihull? I'd rather deal with the vibration.
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Old 16-06-2016, 14:09   #33
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Re: Vibration troubleshooting help

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Originally Posted by F10 View Post
Last question I had is what is the picture actually showing? Is that the packing gland or a dripless gland? It almost looks like a cutlass bearing, but that should not be inside the boat hull.
Hi there, I have heard it called several things. But it is a dripless stern gland.

Beneteau Oceanis 40 - 2008
Mallorca
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Old 16-06-2016, 14:24   #34
F10
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Re: Vibration troubleshooting help

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Originally Posted by AFKASAP View Post
Hi there, I have heard it called several things. But it is a dripless stern gland.

Beneteau Oceanis 40 - 2008
Mallorca
It looks like you might have something like this pic. If so, looks like there is a bearing inside. Maybe that is the problem. If that is the case, you could replace the gland or maybe just bearing, or convert to a stuffing box (that would drip slightly) like buck alogoquin
Bronze Packing Boxes - Self Aligning - Spud Type - Right Hand Thread On Buck Algonquin
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