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Failed Engine Mounts

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Captain Cook View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Captain Cook Quote  Post ReplyReply Direct Link To This Post Posted: 20 June 2017 at 10:48
As I explained to Dråpen in a PM, the nuts are of two different sizes.
The new mount is delivered with a small nut at the bottom of the bolt.
On top of this nut I put a large nut and a washer, then the engine foot, and then a washer, a spring washer and a large nut. All liberally soaked in blue Loctite. (see photos)
The extra large nut I got from the old broken engine mount.

A hint to the correct position of the engine foot/feet can be seen on the technical drawings in the background of two of the photos. here you can see about 8 mm free thread from the foot to the nut.


Edited by Captain Cook - 20 June 2017 at 11:17
Freya H400 #27 (2006), 40HP 3JH4E, 2-cabin, 3-blade Flexofold, Aries LiftUp Windvane, Exturn 300, Jefa DD1,Simrad NX40,Icom M603(VHF)+M802(SSB)
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landlocked View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote landlocked Quote  Post ReplyReply Direct Link To This Post Posted: 16 September 2017 at 19:43
I just noticed this added post from Captain Cook, showing the same type of engine mount failure I had on my Hanse400.   FYI, the original mounts failed after 3 years and the replacement mounts with my slightly modified installation are still good after 8 years.   I still feel that the practice of using threaded studs as a "structural element" that flexes with engine vibration is not good, and they should only be used as a threaded attachment for tightening the engine down onto another structural element such as a standoff (in my case I used an oversized nut).
I often wonder what would have happened if this failure had precipitated something worse, like breaking the third and only remaining engine mount, and/or tearing the rubber seal on the saildrive.
"Kerkyra" 400e #042
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samuel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samuel Quote  Post ReplyReply Direct Link To This Post Posted: 17 September 2017 at 09:48
Surely if one is worried about the length of the stud being such that it a allowed to flex the answer would be to place a steel plate ( a piece of gauge plate being best) under the engine mount so that the engine mount itself was higher. Then one would just put 2 longer bolts into the bed & use less of the top stud.


Edited by samuel - 17 September 2017 at 09:48
Daydream Believer- Hanse 311- No GBR9917T- Bradwell Essex
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landlocked View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote landlocked Quote  Post ReplyReply Direct Link To This Post Posted: 17 September 2017 at 15:38
I don't recommend adding a spacer under the engine mount, and using less of the stud, as this would change the damping effect of the engine mount. Yanmar specifies the height of the fibreglass foundation, the nut location on the stud, and the rating of the rubber material in the mount.   Presumably this is all with consideration of how it will dampen the vibrations for the specific engine and saildrive.   Personally, I would not deviate from that without an endorsement from Yanmar.   
I think that, rather than specify a height for the nut location, Yanmar should supply a standoff at the correct height, which you just insert on the stud. Bolting the engine onto the standoff instead of suspending it on the stud would solve the fatigue problem.
"Kerkyra" 400e #042
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samuel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samuel Quote  Post ReplyReply Direct Link To This Post Posted: 17 September 2017 at 19:18
Originally posted by landlocked landlocked wrote:

I don't recommend adding a spacer under the engine mount, and using less of the stud, as this would change the damping effect of the engine mount. Yanmar specifies the height of the fibreglass foundation, the nut location on the stud, and the rating of the rubber material in the mount.   Presumably this is all with consideration of how it will dampen the vibrations for the specific engine and saildrive.   Personally, I would not deviate from that without an endorsement from Yanmar.   
I think that, rather than specify a height for the nut location, Yanmar should supply a standoff at the correct height, which you just insert on the stud. Bolting the engine onto the standoff instead of suspending it on the stud would solve the fatigue problem.


But in the earlier thread you pointed out that Yanmar's recommendations ( ie threaded stud used as a structural element) did not work because the original installation broke - did it not?
So on that basis one would not really hold a lot of faith with their recommendations!!!


Edited by samuel - 17 September 2017 at 19:24
Daydream Believer- Hanse 311- No GBR9917T- Bradwell Essex
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Post Options Post Options   Thanks (0) Thanks(0)   Quote landlocked Quote  Post ReplyReply Direct Link To This Post Posted: 17 September 2017 at 22:03
Ya, I don't like their recommendations about using the stud as a structural element, because it fatigues and fails, with nasty consequences, on a number of boats.   It seems prudent to take measures to prevent that, and I wish Yanmar would look into this themselves.
I would still stick to their mounting dimensions though, since presumably they've done more engineering work on that than you or I.  I guess I don't see this as a matter of faith, just logic.

"Kerkyra" 400e #042
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Angelina View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Angelina Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2019 at 17:45
Hi All,
Seems to have gone quiet on the failed mounts.
Could someone pls describe how the vibration mounts were changed?
Lift the engine up, unscrew the engine brackets, then
slot in the vibration mount?
Or simply lift the engine high enough with the help of the boom to be able to slide in the vibration mounts without actually having to remove the barely accessable
engine brackets?
Can the saildrive seal take all that lifting of the engine?
Thanks Very much. G.
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landlocked View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote landlocked Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2019 at 18:29
In my case I did this:
1. Removed companionway steps by unscrewing hinges
2. Connected main halyard directly to the hoisting eye on top of the engine
3. Lifted engine enough to slide the two forward mounts out sideways (slide the bottom sideways and drop them out)
4. Reverse process to put in new mounts.

I left the aft mount connected and the amount of movement was small enough that it didn’t strain the saildrive seal or rear mount.  The halyard had a direct line to the engine lifting eye without interfering with anything so I didn’t use the boom, just the direct halyard connection.

I did this three times, first with repaired (welded) mounts as a temporary measure and again when I reached a port where I could buy new mounts, then again when I modified the connection by adding some oversized nuts to serve as standoffs to prevent the fatigue failure of the studs.

Incidentally, I still have the modification in place — It has been like that for 10 years now without problems.
"Kerkyra" 400e #042
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Captain Cook View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Captain Cook Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2019 at 20:24

As you can read in my post above, Yanmar in Denmark tells, that HanseWerft has mounted the engine at the top of the thread, which maybe is the reason for the metal-fatigue.
Anyway, both my engine mounts broke in rough weather, and I had to make a temporary repair. When I recieved the new mounts (In Kiel, 100 Nm from my own harbour), I used a piece of 22 mm plywood (120x20 cm) to support the engine when the mounts were changed. I used another plywood as a lever to lift up the engine when needed. The work lasted a few hours, and did not call for any special skills. Any sailor with one left-, and one right hand should be qualified.
As for your remark  on "barely accessible" mounts, I do not agree, The mounts are easily accessible, just look at my photos above.(I naturally removed the cover under the stairs,-4 screws).
You wonder, if the saildrive seal/diaphragm will survive the movement of the engine. I can inform you, that behind the saildrive there is a third mount, so the engine is not suspended in the diaphragm, when the two mounts are broken.
I changed the diaphragm later on, but I do not know, if Kerkyra did that as well.
I have mentioned earlier, that in the background of a pair of my photos, there is an official drawing from Yanmar, which clearly shows, that the way I mounted the nuts, are correct. There is a gap of 8-10 mm between the flap on the engine and the top nut. That tells you there should be 8-10 mm visible thread over the upper nut. I seem to have lost the drawing, and can not find it again on the net.




Edited by Captain Cook - 03 March 2021 at 09:35
Freya H400 #27 (2006), 40HP 3JH4E, 2-cabin, 3-blade Flexofold, Aries LiftUp Windvane, Exturn 300, Jefa DD1,Simrad NX40,Icom M603(VHF)+M802(SSB)
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Angelina View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Angelina Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2019 at 07:02
Guys,
I am new here.
Did not intend any harm.
Asked a simple question in reply to a post.
Appreciate all that participate and take the trouble to write.
I do have the same problem, boat built ‘09 and in the water since.
No further required or of interest?
PM if you like.
Even if I was a troll, so what?
This forum is to relay information. To whom it may concern.
Let’s sail. Or try to!
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