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Go Back   SailNet Community > On Board > Gear & Maintenance > Need help YANMAR engine mount
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Thread: Need help YANMAR engine mount Reply to Thread
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Topic Review (Newest First)
04-15-2010 02:15 PM
Kerkyra
Update on Yanmar mounts

FYI: Just thought I'd update this to say that my modified mounts are still OK, and that I never received a reply from Yanmar when I sent them a description and photos about this problem.

I strongly beleive that this is a design flaw that should have been fixed long ago - has anybody else had this problem?
07-28-2009 12:52 AM
Kerkyra I just returned from a vacation on our Hanse 400, which also has a 3JH4E with SD50 saildrive. Our first day out we noticed the engine sounded different and I went below to find the engine was hopping around and both mounts had failed. I limped into port and was lucky to find a mechanic to weld on some replacement studs to hold the engine until I got some replacements a few days later.

The failure was very similar to what was described by Giulietta in the original post, except both studs had failed immediately below the nut that supports the engine (not between the nut and the engine tab). I've tried unsuccessfully to upload some photos (800x600, <50kB). Our engine was also delivered in 2006 and has 900 hours on it.

I showed the photos to a mechanical engineer who had the same comments that "Bob" had earlier in this thread. He too was surprised that the stud itself was used to support the vibrating load instead of some kind of spacer. He explained that threaded rods are subject to failure fatigue if they are subjected to flexing as these ones would be. The threads weaken the rod because the strain isn't evenly distributed across the rod but is greater on the "inside" surface of the thread and less on the "outside" surface. (similar to the effect of a small nick in a wire that will cause it to fail by focussing the strain in one spot).

This explanation made very good sense to me and it was very interesting to read the corroborating explanation and same suggested solution from Bob. The diagram in the original post doesn't quite make as much sense to me because the rod wouldn't flex so much at the interface of the nut and the engine tab (could it be that the drawing is not quite right?)

If the engine was bolted directly to the mount or if a spacer was placed between the engine and mount then the threaded stud would only function as a fastener and not a standoff and would not be subject to this failure mode.

I'll be sending some photos to Yanmar. One would hope that they have seen enough of this failure to realize there is a flaw to be addressed - perhaps with a field upgrade to add a standoff between the mount and the engine tab. I improvised one with my replacement mounts because otherwise I have no reason to trust that this won't happen again. I found some oversized stainless nuts which I placed between the top of the mount and the lowest nut (the nut that holds the stud on the mount), with a washer in-between. This provides the same spacing as the original installation but essentially creates a "stack" between the engine and the mount, with the stud used only to hold it together. (again, I have a photo but can't upload it).

I was very happy to see Bob making the same suggestion so hopefully I've made an improvement. I think he is bang on with his comment about using threaded fasteners for structural members.

Thanks very much to SailNet, and to Giulietta, Bob and Quiksilver and others for sharing their information and insights.
09-18-2007 07:25 PM
Giulietta
Quote:
Originally Posted by theartfuldodger View Post
such a break is a defective bolt, for the real break if not installed right would have been at the mount, this happens alot in the automotive industry, and after test performed by labs, the bolt was not harden right. If you wish to know my experience 35 years in the automotive industry, heavy equioment and marine as well. I myself installed new engine in my 33 O/I Morgan two years ago, and works very good, thanks to Yanmars retrofit kit.

S/V The Artful Dodger
Thanks for your input..that was my initial idea, but they said otherwise..

anyway...all is fine now...
09-18-2007 07:19 PM
theartfuldodger such a break is a defective bolt, for the real break if not installed right would have been at the mount, this happens alot in the automotive industry, and after test performed by labs, the bolt was not harden right. If you wish to know my experience 35 years in the automotive industry, heavy equioment and marine as well. I myself installed new engine in my 33 O/I Morgan two years ago, and works very good, thanks to Yanmars retrofit kit.

S/V The Artful Dodger
09-18-2007 07:06 PM
Giulietta ahhhh that was funny...but what would I do with a Catalina???

Be just one more guy with a Catalina???

I like being different...and believe me, many more things will break starting in November..that's a guarantee

By the way...can a Catalina do it???
09-18-2007 06:58 PM
jackytdunaway Broken boom, broken engine mount stud, who knows what else. Trade it in for a Catalina. CD can help you find one.
09-18-2007 06:13 PM
Giulietta They took it to send it to the manufacturer in Japan, to complete the complaint/guarantee thing.

I didn't want it any way.

Everything seems normal now, and I'm happy
09-18-2007 05:24 PM
Rockter I would buy a spare mount, or two, and watch the others.

Interesting that they took the old one away with them.
09-18-2007 04:33 PM
camaraderie I don't think the sail drive was meant for going 15 knots...the force of the water torqued the whole engine and broke your mount! (g)
09-18-2007 03:16 PM
Giulietta My engine mount (only one broke) broke in November 2006, after 150 hours in service. And we had sailed in pretty high seas and winds with the engine on for 20 minutes, which I believe its when it broke..luckily never had problems with the saildrive leak...

Anyway, the new mount was installed right then, and since then my engine only worked 50 more hours, most of them sailng the boat to where it is now in July.

So far so good, and I do check them periodically...

Thanks for sharing and explaining your case..I will transmit it to my Yanmar friends.

Why didn't you stop in Portugal to repair?? Yanmar here is very good.
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