Failed Engine Mounts

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   If you are in doubt if broken engine mounts could sink your boat, read this link:

https://www.sailnet.com/threads/need-help-yanmar-engine-mount.25659/

A cat sailor is telling this: "..... the two
mounts of both engines broke at exact same place on the studs, leading to a
broken and severely leaking saildrive double seal on SB engine due to twisting”
:Kjeld

Edited by Captain Cook - 09 March 2024 at 22:40

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Captain Cook Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 23 May 2006 Location: Denmark Status: Offline Points: 1245	Post Options Post Reply Quote Captain Cook Report Post Thanks(0) Quote Reply Posted: 09 March 2024 at 09:47
	If you are in doubt if broken engine mounts could sink your boat, read this link: https://www.sailnet.com/threads/need-help-yanmar-engine-mount.25659/ A cat sailor is telling this: "..... the two mounts of both engines broke at exact same place on the studs, leading to a broken and severely leaking saildrive double seal on SB engine due to twisting” :Kjeld Edited by Captain Cook - 09 March 2024 at 22:40
	Freya H400 #27 (2006),2-cabin, 40HP 3JH4E, 3-blade Flexofold, Aries LiftUp Windvane, Exturn 300, Jefa DD1,Simrad NX40,Icom M603(VHF)+M802(SSB)

Sportswagoneer Members Profile Send Private Message Find Members Posts Add to Buddy List Lieutenant Commander Joined: 17 June 2018 Location: Norway Status: Offline Points: 77	Post Options Post Reply Quote Sportswagoneer Report Post Thanks(0) Quote Reply Posted: 09 March 2024 at 10:14
	Thanks for contributing your experience! I have seen a few YouTube videos of engine mount replacements now - and it really looks fairly straight forward. An alternative to suspending the engine from a halyard would be to support it from below with wooden blocks or even a standard car jack. Any comments on that? Also - all the videos are from boats with straight propeller shafts rather than sail drives. As I understand it, sail drives should be quite a lot easier since we don’t need to disconnect the transmission coupling and thus there’s no alignment. BUT: There must be SOME alignment? How do you know that the engine is properly elevated/aligned? You can copy the height from the old mounts - but if Hanse mounted them too high, maybe they should be adjusted? Also: What about the rear mount at the sail drive? (3JH5e + SD50) Can’t find a video of that and it seems different from the others. Anyone replaced that and have comments on accessibility in a H400 and on alignment and replacement procedure?
	2010 Hanse 400 #700 “Neste Sommer”

H8jer Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 14 September 2010 Location: Denmark Status: Offline Points: 1503	Post Options Post Reply Quote H8jer Report Post Thanks(0) Quote Reply Posted: 09 March 2024 at 14:35
	Arrrh Another item to the to-do list! Just went to my Hanse 370 with a 3YM30 engine. I have always wondered why my saildrive appeared to point more downward then other boats with same engine... Edited by H8jer - 09 March 2024 at 14:36
	Hanse 370#487 30HP 3-cabin

landlocked Members Profile Send Private Message Find Members Posts Add to Buddy List Rear Admiral Joined: 12 April 2005 Location: Canada Status: Offline Points: 568	Post Options Post Reply Quote landlocked Report Post Thanks(0) Quote Reply Posted: 09 March 2024 at 16:12
	Yanmar may be able to provide the spec for the proper mounting height on your 370. The height you show in the photo is similar to my 400 and this was the height specified by Yanmar. They use this threaded stud as a means for adjusting the mounting height which unfortunately leads to stress fractures forming in the thread leading to a failure of the mount. In other words, it’s “supposed to be” secured at a specified height, not directly on top of the mount so you might want to check first if you are thinking of moving it. Once you’re sure of the proper height you may want to make a modification as I and others have shown on this site, to prevent the threaded rod from failing. I think that instead of using a nut to support the engine on the threaded rod, Yanmar should offer some standoffs that can be slipped over the rod after cutting to the specified height, then the rod is only clamping the engine onto the stand-off and not subjected to the torsional stresses. I have found Yanmar service to be fairly responsive and they’ve been helpful with other issues but when it comes to this common failure mode for the mounts they do not admit to any flaw in the design, and just told me “our mounts don’t break”, so unfortunately they are doing nothing to protect their customers. Edited by landlocked - 09 March 2024 at 16:13
	"Kerkyra" 400e #042

Captain Cook Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 23 May 2006 Location: Denmark Status: Offline Points: 1245	Post Options Post Reply Quote Captain Cook Report Post Thanks(0) Quote Reply Posted: 09 March 2024 at 16:57
	In a photo on page one of this subject, you can see a Yanmar technical drawing of an engine mount in the background. From this I deduct, that there is supposed to be 8-10 mm of visible thread above the upper nut. Also the danish Yanmar agent mentioned that this was the correct placement on the mount. Anyway, twelve years ago I lowered the front of the engine with those 8-10 mm, and the engine mounts I fitted then are still going strong. The mounts fitted by Hanse Werft lasted only half that time (by Landlocked only 3 years). The difference between Landlocked´s solution and mine, are those 8-10 mm, and the fact, that Landlocked´s lower nut is larger than the thread. The nuts on my engine mount are soaked in Locktite, and tightened to the thread. Obviously I like my own handiwork best, but I suggest, that all Hanse-owners choose to strenghten the bolts on the engine mounts, by adding a few extra nuts, using Landlocked´s method or mine. Fitting a piece of wire with wire-clamps (photos page 1+3+4) may also be a good idea. :Kjeld (I imagine that you took your time to read all the pages of this subject?) Edited by Captain Cook - 14 March 2024 at 09:39
	Freya H400 #27 (2006),2-cabin, 40HP 3JH4E, 3-blade Flexofold, Aries LiftUp Windvane, Exturn 300, Jefa DD1,Simrad NX40,Icom M603(VHF)+M802(SSB)

sgrhma2 Members Profile Send Private Message Find Members Posts Add to Buddy List Captain Joined: 20 November 2021 Location: Northern Irelan Status: Offline Points: 271	Post Options Post Reply Quote sgrhma2 Report Post Thanks(1) Quote Reply Posted: 09 March 2024 at 19:03
	Kjeld is absolutely correct, the lower the engine is mounted down the stud the less the bending moment on it and as such there will be an increase in cycles before fatigue failure for a given stud cross sectional area. All the lower nut does is set the height the engine sits at. Unlike a boat with a shaft drive, a boat that has a saildrive does not need alignment, it only needs mounting in a way that doesn’t stress its diaphragm. If you look at the full range of locational positions that are available in the engine mounts, at none of them is the diaphragm in any danger of being stressed, with plenty of flex still in it available to accommodate extreme movement within the engine mounts. Using additional lower nuts or an oversize one below do nothing for strength, but crucial they act as height shims and increase the effective csa of the stud. If you wanted to you could completely do away entirely with the lower nut and use a series of shims (1, 3, 6, 10mm steel) to set the chosen height of the engine and tighten down the top nut. If you want to go down this route and make your own shims, I would make them square based on the width dimension of the top of the mount and drill the hole 0.5 - 1.0mm larger than the stud diameter. The reason why the mounts will resist stud failure when shims are used is because the bending moment is over a larger csa and similarly the increased area of the shim will eliminate any flexing in the stud itself which causes fatigue cycles. No matter what you do, as Kjeld has done, fitting a wire as back up is an extremely good thing to do. For those of you that have had failures, it would be very interesting to know what the engine hours were when failure occurred. I would expect that boats fitted with the 40hp engine all have lower hours that failures with ones fitted with a 30hp. The higher mass of the 40hp engine creating higher load fatigue cycles, hence lower potential hours before failure. This doesn’t mean you’re off the hook if you have a 30hp, just slightly longer before fatigue catches up with them. For me what it means is I’m going to check my mounts again and probably make a set of shims. As to why Yanmar make the mounts the way they do, is simply a case of one set of mounts will work with a saildrive and have the necessary fine adjustment required for shaft alignment. What they provide is a lot cheaper than supplying shims to cover all necessary instalment heights. A simple fix for them would be to use a larger diameter stud, increasing is csa and resistance to fatigue. Hope this is useful Simon

landlocked Members Profile Send Private Message Find Members Posts Add to Buddy List Rear Admiral Joined: 12 April 2005 Location: Canada Status: Offline Points: 568	Post Options Post Reply Quote landlocked Report Post Thanks(0) Quote Reply Posted: 09 March 2024 at 20:11
	The key is to avoid dynamic loading of the threaded rod, because the stress is greatly amplified in the thread root (compared to solid rod). So you need something to stabilize the rod from bending and transfer the torsional forces to the rubber mount. Threaded rods are not supposed to be used for holding dynamic loads because of this stress concentration in the root which leads to fatigue failure. Ideally you want only tension on the rods.
	"Kerkyra" 400e #042

sgrhma2 Members Profile Send Private Message Find Members Posts Add to Buddy List Captain Joined: 20 November 2021 Location: Northern Irelan Status: Offline Points: 271	Post Options Post Reply Quote sgrhma2 Report Post Thanks(0) Quote Reply Posted: 09 March 2024 at 20:15
	Landlocked, you are absolutely correct, and is indeed why shims work with the standard mount. Simon

Captain Cook Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 23 May 2006 Location: Denmark Status: Offline Points: 1245	Post Options Post Reply Quote Captain Cook Report Post Thanks(1) Quote Reply Posted: 10 March 2024 at 10:46
	Here are links to the Yanmar official method of placing the engine brackets in the Yanmar engine mount. https://uploads.tapatalk-cdn.com/files-2540/1581764097_YanmarEngineMounts.pdf https://www.manualslib.com/manual/1063627/Yanmar-3ym30.html?page=21#manual Notice the text: "On all models, try and keep the engine foot or bracket closer to lower end of dimension 'H' if possible." ................. since the difference between the higher and lower end of "H" is 10 mm, I could say, that is exactly what I have done :-) (Lowered the bracket 8-10 mm). In all of my posts I am talking of engines with SAILDRIVE. A fixed propeller shaft needs to be adjusted to 1/10 mm, where the saildrive is more flexible. My 3JH4E came with the "200" engine mount. If you check out the homepage of Ellebogen: https://ellebogen.com/us/yanmar-engine-mount-replacement-marine-engine-yanmar-2gm20/ ( update: Just noticed that they sell a set of 3 mounts for my boat) You will notice, that Ellebogen have stacked the nuts just like I have. If one has to follow the instructions from Yanmar, the mantra from Ellebogen about max. 7 mm of thread visible may not be possible. I believe, that NO thread at all should be visible under the bracket, and Ellebogen also shows this with stacked nuts. This discussion (just like the subject of smouldering seacocks) is a matter of some importance, because in the worst case scenario the rubber diaphragm could be torn out of the boat, and then a liferaft would be nice to have. So, Fellow myhansers, just like H8jer is planning, buy 4 nuts (M16x1,5), a tube of Locktite, a piece of steel wire and four wire clamps. In this case the added security costs less than a semi-bad bottle of Lalande de Pomerol. :Kjeld Edited by Captain Cook - 10 March 2024 at 23:27
	Freya H400 #27 (2006),2-cabin, 40HP 3JH4E, 3-blade Flexofold, Aries LiftUp Windvane, Exturn 300, Jefa DD1,Simrad NX40,Icom M603(VHF)+M802(SSB)

H8jer Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 14 September 2010 Location: Denmark Status: Offline Points: 1503	Post Options Post Reply Quote H8jer Report Post Thanks(0) Quote Reply Posted: 10 March 2024 at 11:40
	Hi Kjeld I am getting a quote for new engine-mounts because my engine just passed 1000h and are perhaps 14 years old. I think my engine mounts looks fatigued compared to your mounts. The height above the rubber looks to be less than yours. Last season we also had an experience where we had to lower the engine rpm due to excessive vibration. It felt like seaweed in the propeller but going a bit in reverse didn't fix the issue. Afterwards the propeller was inspected an it had no growth or any issues. Perhaps the engine starts shaking and the mounts metal parts touch and the rubber can no longer smoothen out the vibrations. So I will get new mounts and also add nuts so no threads are visible.
	Hanse 370#487 30HP 3-cabin



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