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Old 05-12-2008, 23:41   #1
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Engine Mountings - are they knockdown proof ?

My vessel underwent an annual safety inspection last week and the inspector raised one question / finding "check that your Yanmar engine mountings are rool over proof". Looking at the mountings I could not see how they would not part if the vessel was on its side or worse upside down. I contacted Yanmar and the agent replied
"Yanmar Europe advised me that this is a very unusual question, but they have notified me that the engine mountings used on all the Yanmar engines is for pleasure usage and do not require certification.
They advised me that if you anticipate that you are going to roll over and require certified engine mounts that can do so that you should look at sourcing Dunlop type engine mounts."

How does the rest of the world cater for this ?
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Old 06-12-2008, 00:04   #2
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Ahh... the very same question I have ben asking for several years now and to date I have not received a clear answer. I should have thought to do what you have done - which is to ask the collective wisdom of the CF.

Thanks A N C.

In my case, the engine is a 2GM20 with Yanmar supplied mounts. What is your engine?
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Old 06-12-2008, 06:01   #3
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Quote:
How does the rest of the world cater for this ?
I think the issue is that you asked Yanmar a question that they interpreted to mean you needed to have the mounts "officially certified" as part of your inspection. The other way to look at it is the inspector posed a question and he obviously didn't know the answer. He looked at it and he still didn't know. I'm not sure a bunch of forum members that never saw the boat will know any more.

It is possible the mounts will handle a total rollover but that does not speak to if the mounts could be disconnected from the boat. The mounts themselves would not have to fail. The mountings could be perfectly connected to engine with no damage yet not connected to the boat. It's a huge difference even if the result would be effectively the same. It's also possible that the hull could break up and the engine would go to the deep still attached to a piece of the hull. That result in this narrow context is preferable but not in the overall goal of vessel integrity.

I think it would be fair to say Yanmar has no intention of providing "certification" as to the ability of their engine to be held in place by another companies method of installing the mounts. It is unfair to ask them. You got what I would expect to be the answer - they can't know if the mounts will secure the engine in a knockdown.

Just how hard do you expect to be knocked? I would venture you could easily soak the masthead without the engine coming loose. The possibilities for everything else in the boat including the crew are pretty much limitless. Going keel up with a rogue wave smashing on top of you might not matter if the engine is held in place since the boat might not still be there either.
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Old 06-12-2008, 07:05   #4
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Here is about everything you need to know about mounts except how much weight they will hold. http://www.anti-vibration-mounts.net/tech-info.pdf

and you can get that here Marine Engine Mounts by clicking on the individual mount.

If one has a mount that is old/lots of hours or rusty it cannot really be trusted. An off-shore boat SHOULD always have fairly new mounts adequate to support a motor for a number of years.

This is what I have on mine which will hold 450-750# upside-down, multiplied X 4 = 1800-3000#, which is more then enough for a 50 hp diesel of 650#, But when you add the wear and tear of thousands of hours and being tossed P/S with the twisting of the shaft it doesn't take long for the mounts to break down.



A quick inspection of the rubber in the mounts will tell all. Any cracking is a sign of degeneration and SHOULD be considered for replacement.

Like stated above, any certs would have to be through the dealer with their own equipment installed and within their own time rating.
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Old 06-12-2008, 08:14   #5
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I've read discussions in other places as to whether the engine mounts will keep the engine in place if the rubber part of the mount fails.

I assume that this is what they are talking about:

3. Fail safe design using steel rebound control washer

From:
R and D MARINE : Marine Engine Mountings

Here's another brand
http://www.henleyspropellers.com/iso...ine_mounts.htm

The same discussions have said that some of them used wire rope to create a fail safe for their engine mounts.


I have a friend that got a fishing net in his prop. His old oil soaked mounts failed, the engine slid aft and the prop jammed his rudder hard over.

John
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Old 06-12-2008, 09:27   #6
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Quote:
I've read discussions in other places as to whether the engine mounts will keep the engine in place if the rubber part of the mount fails.
When they start to break down there becomes a better chance you'll lose the shaft coupling and of course the shaft alignment. Many couplings break loose rather than allow the bad alignment to do more damage. It's cheaper and easier than replacing a cutlass bearing.

This can be apparent should even one of the mounts start to break down. They don't have to break loose to have a problem. Once the alignment gets trashed you can run up some serious damage and everything is still connected. If you change one mount it's best to do them all then realign the shaft. Rapacking the stuffing box as well.
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Old 06-12-2008, 09:40   #7
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Originally Posted by Pblais View Post
When they start to break down there becomes a better chance you'll lose the shaft coupling and of course the shaft alignment. Many couplings break loose rather than allow the bad alignment to do more damage. It's cheaper and easier than replacing a cutlass bearing.

This can be apparent should even one of the mounts start to break down. They don't have to break loose to have a problem. Once the alignment gets trashed you can run up some serious damage and everything is still connected. If you change one mount it's best to do them all then realign the shaft. Rapacking the stuffing box as well.
I think that their concern is 500 lbs of engine flying around the cabin while you're upside down.

John
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Old 06-12-2008, 10:05   #8
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Originally Posted by Wotname View Post
Ahh... the very same question I have ben asking for several years now and to date I have not received a clear answer. I should have thought to do what you have done - which is to ask the collective wisdom of the CF.

Thanks A N C.

In my case, the engine is a 2GM20 with Yanmar supplied mounts. What is your engine?

It is a Yanmar 4JH2E also Yanmar mountings - glad someone else has been wondering. I will post a picture tomorrow but they are brand new and once upside down I cannot see how the composite rubber will hold the engine in place.
Regards Alan
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Old 06-12-2008, 10:06   #9
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Originally Posted by cal40john View Post
I think that their concern is 500 lbs of engine flying around the cabin while you're upside down.

John

Exactly my concern !
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Old 06-12-2008, 10:13   #10
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[quote=Pblais;230442]I think the issue is that you asked Yanmar a question that they interpreted to mean you needed to have the mounts "officially certified" as part of your inspection.

I took great care when asking Yanmar not to mention "certification" as this has certain implications for a manufacturer - I agree with your views. I will contact them again and let them know I do not require them certified but simply want to know if there is a reasonable cahnce that the engine will not break free in a knock down.

Regards Alan
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Old 06-12-2008, 10:16   #11
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I was just thinking that a loose loop of cable that is crimped around each motor mount would work as a backup for a failed motor mount. Its not a replacement of course but if the boat did go inverted and the mount did fail, the engine would not be going anywhere. I have never seen this done though.

Its pretty much a don't worry about it kind of thing though. If you roll you have more important things to worry about.
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Old 06-12-2008, 11:33   #12
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military/CG boats require a cable to secure the engine. It can be done many ways but one on each end/each side should be fine. Personally I doubt that 4 good mounts as well as the shaft coupling would allow the engine to come free, but anything is possible. Those mounts are incredibly strong.
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Old 06-12-2008, 12:28   #13
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............... as the shaft coupling would allow the engine to come free, but anything is possible.
One problem is the quality of the shaft log. Some glass boats have a glass shaft log. If it gets torn up the boats going down unless someone is quick to stuffing the leak and that's not likely in a rough sea with the motor still bouncing around.

It's better to keep the mounts in good shape. Putting cables around a mount would have to be mounted just as strong, if not, more so then the MM themselves to survive a loose motor. Once stuff starts moving around in a rough sea it's nearly impossible to get it secured, especially if it's heavy.
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Old 06-12-2008, 12:33   #14
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The mounts that are pictured in DelMarrey's thread are the ones I use and I have complete faith in them. I am more concerned as to how they are bolted to the engine bed and what happens if the wood/glass/steel or bolts in the engine bed are deteriorated. I've thought of a cable or chain from the leg of the engine mount to a bolt through the sides of the bed to be a good idea but haven't installed it yet.
Kind regards,
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Old 06-12-2008, 12:36   #15
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Originally Posted by Cheechako View Post
military/CG boats require a cable to secure the engine. It can be done many ways but one on each end/each side should be fine. Personally I doubt that 4 good mounts as well as the shaft coupling would allow the engine to come free, but anything is possible. Those mounts are incredibly strong.

I have been informed that this is the best solution - 4 cables - one around each mounting.
Many thanks Alan
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