# yanmar motor mount replacement idea



## scottyt (Jul 19, 2008)

okay i read a thread somewhere about someone replacing their motor mounts, they did not use yanmar mounts. on the replacements they used the studs where too short, so they used rubber vibration sheet to bump up the height a little. Raw Materials > Rubber > Sheets and Strips > Rubber,Buna-N,1/2 In Thick,2 x 36 In : Grainger Industrial Supply

so i thought why not replace the rubber in the mount with it. a few problems but not many mostly it is not going to be glued to the mount like the stock rubber. but hey we own things called bolts.

here is my idea, cut scrape what ever the old rubber out. then replace it with stacked layers of the rubber to the right height. now to hold it in place use a pin ( pictured in red below ) welded to the upper steel part, which fits in tight holes drilled in the rubber. these pins basicly align and center the rubber to the mount. then use bolts thru tightly drilled holes thru the rubber, with the hole thru the upper metal mount drilled larger to give room to viberate with touching the bolt. it would require stacks of rubber on top too with plates for the bolt heads to bear on.

what does every one think, it works out that all four mounts can be rebuilt for under 50 bucks vrs over a 100 per stock mount.

okay pics first a stock mount










now a paint drawing of my idea
black stock steel parts ( sort of )
gray rubber sheet
red alignment pins
orange bolts
blue backing plate


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## scottyt (Jul 19, 2008)

now i know my drawing does not look just like the yanmar but you should get the idea, i drew it to be simple to look at and understand it


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## funsailthekeys (May 15, 2008)

They don't cost that much to go thru all that trouble.


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## scottyt (Jul 19, 2008)

funsailthekeys said:


> They don't cost that much to go thru all that trouble.


well in the current market my income has come down about 50 %, 400 bucks is a weeks income


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## funsailthekeys (May 15, 2008)

*$400.00*

I was thinking more along the lines of the damage that might happen if they didn't work out. Just to haul my boat out for anything is close to $600.00.Not that it was a bad idea.


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## captbillc (Jul 31, 2008)

*yanmar engine mounts*

the yanmar mounts are designed to cut down on vibration transmitted to the hull. when they design them they have to figure in the weight of the engine & transmission, also the thrust from the propellor. it would be hard for an individual to duplicate this, it is better to get the correct mounts.


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## k1vsk (Jul 16, 2001)

All too often, people tend to take the cheap route and find it to be a false economy resulting in an even greater expense later. Yo do it properly, the mounts have different specs depending on which side of the engine they are intended - how would anyone replicate that?
More important, the question arises - what difference does it make and what are the consequences of doing it wrong?


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## rikhall (Feb 7, 2008)

The Yanmar mounts are also different for the front and back of the motor.


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## motovationcycles (Dec 2, 2008)

*mounts*

Not worth it, get the factory mounts. Pretty cheap in the scheme of sailing things. Also the bolts will transmit vibrations from the motor to the engine bed. I have seen this tried before. There are always mounts on E-bay for cheap.


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## Omatako (Sep 14, 2003)

captbillc said:


> the yanmar mounts are designed to cut down on vibration transmitted to the hull. when they design them they have to figure in the weight of the engine & transmission, also the thrust from the propellor. it would be hard for an individual to duplicate this, it is better to get the correct mounts.


Yep, I agree. The propellor is commonly believed to push the boat but in fact the propellor pushes the engine/gearbox which in turn pushes the boat.

The connection between the engine and the boat (the mountings) gets a whole lot more energy through it than is normally understood. If the mobility (or lack thereof) of the mounting is compromised, the whole drive line integrity goes with it and then you get vibrations (from both the bolt contact as well as the shaft misalignment), water leaks, stress cracks, etc.

No, I reckon the money you save by making up Heath-Robinson mountings will be burned away very quickly in additional maintenance. Get the real thing.


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## k1vsk (Jul 16, 2001)

Omatako said:


> The connection between the engine and the boat (the mountings) gets a whole lot more energy through it than is normally understood. If the mobility (or lack thereof) of the mounting is compromised, the whole drive line integrity goes with it and then you get vibrations (from both the bolt contact as well as the shaft misalignment), water leaks, stress cracks, etc.


I would agree that the integrity of the mounts is critical, however, this still doesn't answer my question - as long as someone, such as the OP, can make a mount which is structurally secure and which minimizes vibration, what difference does it make who constructs it?
This type of fabrication isn't "rocket science".


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## TheFrog (Oct 25, 2007)

k1vsk said:


> I would agree that the integrity of the mounts is critical, however, this still doesn't answer my question - as long as someone, such as the OP, can make a mount which is structurally secure and which minimizes vibration, what difference does it make who constructs it?
> This type of fabrication isn't "rocket science".


Funny that we are sitting here in a cold winter day sort of like a day in 1986 when a rubber part on a rocket failed with catastrophic results. Unfortunately, getting vibration damping and force transmission correct on a system like this is a bit like rocket science. Yes, you can make up a rubber mount of your own. No, without many equations, prototypes, and modifications will you get it as good as the Yanmar mounts. They have spent years designing them and using force gauges to make sure it works right. Somewhere in the back of my mechanical engineering mind lies the training to do this work - but I wouldn't bother spending the many hours to attempt it.
Remember the lesson from Challenger - what works right on your drawing board may act differently when hot or cold or soaked in diesel or after 10 years in your engine compartment.


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## jjns (Jul 8, 2007)

You are right, it isn't rocket science. Or brain surgery.
That said. In the picture of the factory mount you may notice that there are no through bolts between the bottom and top plates. The reason is because you have an engineered rubber composite of very specific compound that is chemically bonded to the plates. There is no way you can replicate that bond in your garage, it does require special equipment. Also your idea of individual stacked layers of rubber will not come close to dealing with the torsional loads the mounts will see. As everyone has already said, it isn't about how much you will save but more about how much damage you will do to your boat. Do you really want to save a couple of hundred dollars and end up destroying the trans or engine or mounting bed or maybe all 3? 
You are probably better off leaving the old worn mounts in place then trying to 'build' something that is poorly engineered. Some things just aren't worth short-cutting.
For the record, when I was young and broke and had a broken engine mount on my car, I tried many ways of getting around buying a new one, all of my attempts failed miserably and in the process managed to trash all the other mounts due to the increased loads on them. 
My solution to save a few bucks cost me a bundle.
I am guessing your boat is probably worth a proper repair.


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## Maine Sail (Jan 6, 2003)

jjns said:


> You are right, it isn't rocket science. Or brain surgery.
> That said. In the picture of the factory mount you may notice that there are no through bolts between the bottom and top plates.


Yes and sandwiching rubber strips, that are going to move, will eventually sheer the heads right off the bolts and the whole mount will fail. Also Murphy is always waiting for you so this will of course happen at the most inopportune time..

As others have said these mounts have a lot more science in them than cutting a couple of floor mats up and bolting them together.. Yanmar mounts are free floating with NO bolts penetrating the rubber let alone four or six of them. They are designed to move more in certain directions and less in others. The rubber mount is engineered and designed to allow the torque to be transferred appropriately and not cause damage to other components.

The phrase "penney wise & pound foolish" comes to mind on this forum quite a bit and this thread is no different..


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## timebandit (Sep 18, 2002)

I have motor mounts for engines puting out over 3,000hp but the loads were in just one direction.

Because these mounts must take a thrust load and if it does not bad things will happen.

I vote for the factory ones for that reason.

ON SECOND THOUGHT----BUILD THEM.
YOUR DESIGN WILL WORK
IF YOU GET TO MUCH ENGINE SHAKES TO MUCH THEN YOU CAN SAVE UP FOR THE FACTORY ONES.

I would try to keep the installed hight the same for engine alignment.


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## Giulietta (Nov 14, 2006)

I have had a failure on one of my mounts, in the 1st month, but it was the stud that failed due to over torque on instrallation.

Don't forget that marine engines also have stress side when the boat is powered, and is sailing, higher heel angles.

also, Saildrive engines only have support in the front of the engine, the rear supports are repalced by the support provided by the saildrive.

Since this is a critical issue, I go with original stuff..The seal on the SD may get damaged, then no good complaining to the factory.


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## scottyt (Jul 19, 2008)

i would definitely keeps the alignment issues the same. not trying to convince anyone, but my idea would have about a 1/4 in any direction except up before the bolts hit. i am also not saying it would work, but i know i need at least 1. i also need to do my shaft seal and i dont have the room to back off the nut ( labout a 1/4 inch to the plate on the shaft ) so i need to pull the engine. so while i pull it out i am going to do all four and realign everything. right now when i hell to starboard the engine really shakes


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## ecsimonson (Apr 22, 2008)

scottyt said:


> what does every one think, it works out that all four mounts can be rebuilt for under 50 bucks vrs over a 100 per stock mount.


I'm all for diy stuff but for this bite the bullet and buy the real ones. What happens if all 4 give way when you need the power for whatever reason and gun it? Rotating heavy stuff scares me, especially close to fiberglass that keeps the water out.


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## timebandit (Sep 18, 2002)

Scottyt's engine will be held in place with 16 bolts with his designed mounts.

Your engine is held in with glue.

Wich one would you want to have if your boat was rolled and all the weight of your engine and trans was hanging on them, rubber and glue or bolts?



ecsimonson said:


> I'm all for diy stuff but for this bite the bullet and buy the real ones. What happens if all 4 give way when you need the power for whatever reason and gun it? Rotating heavy stuff scares me, especially close to fiberglass that keeps the water out.


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## timebandit (Sep 18, 2002)

Scottyt
If you haven't sourced your rubber I would recommend going to a truck parts store and getting a truck mud flap.

Get one that has a couple of belts of material in them and you will avoid any stretch and will hold your pin and bolts in perfect location.

The flaps are made from conveyor belting and are very tuff.


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## timebandit (Sep 18, 2002)

In what world would you want your motor to move??

Does your shaft move to match??

Drill your holes in the rubber the size of the bolt and pin and lube with soapy water to install with a tight fit.

You might add a rubber and plate under the nuts though.



scottyt said:


> i would definitely keeps the alignment issues the same. not trying to convince anyone, but my idea would have about a 1/4 in any direction except up before the bolts hit. i am also not saying it would work, but i know i need at least 1. i also need to do my shaft seal and i dont have the room to back off the nut ( labout a 1/4 inch to the plate on the shaft ) so i need to pull the engine. so while i pull it out i am going to do all four and realign everything. right now when i hell to starboard the engine really shakes


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## RKelsall (Jul 24, 2008)

*Not all rubber is equal*

As a polymer chemist I would strongly recommend that you do not try to make your own composite engine mount. There are many many types of rubber and when added to the many types of reinforement materials hundreds of different composits all with their own properties and uses. In tire manufacture ,for example, you will find that different tires use different types of rubber to achieve different results. A tire that uses Butyl rubber will have a very nice smooth ride but very poor gas mileage. The manufacturer has researched the composite used for this application and in fact is probably using different materials for the different locations on the engine to achieve the best possible performance. The idea of making your own mount may seem to offer a cost savings but in fact is probably at very high risk of incurring expensive repairs down the road.


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## jjns (Jul 8, 2007)

TimeBandit

What do you have against Scottyt. Your 'help' will get him killed.

Motor mounts should NEVER be through-bolted, period. 

For a bolt to have strength it must be tight, rubber will compress, if he gets them tight the rubber will be fully compressed and any load will just cause the rubber to tear.

Ever seen a car that has been rolled? Engines rarely fall out, unless SEVERE impact is involved. 

I would be much more worried about the engine breaking free and flailing around with only the prop-shaft to hold it in place.

It would be one of the quickest ways to the bottom of the sea.


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## Maine Sail (Jan 6, 2003)

timebandit said:


> Scottyt
> If you haven't sourced your rubber I would recommend going to a truck parts store and getting a truck mud flap.
> 
> Get one that has a couple of belts of material in them and you will avoid any stretch and will hold your pin and bolts in perfect location.
> ...


Scott,

Please, please do not listen to advice like this. It seems you are going to do this any way and you came here more for reinforcement, than an answer. You overwhelmingly did not get reinforcement for your idea except from a guy advising the use of mud flaps..

Go ahead it's your boat and your wallet but mark my words your mount design will fail and it will likely case damage to other associated items like your drive line or tranny. Yanmar mounts are very well engineered your design is about a Rube Goldberg as it gets. Sorry to be so blunt but after 35 plus years in boating, including working in boat yards when I was younger, I have not once seen someone "re-invent the wheel" with the ultimate outcome to save money and cheap out, and seen it not cause problems in the future. I have seen folks save money on ball valves by purchasing them at Home Depot and then their boat sinks..

This WILL cost you more than buying the original mounts in the long run but you clearly already have all the answers. You've received good advice here, including advice from a chemist who does this stuff for a living yet your in bed with a guy who thinks using truck mud flaps on a 10k engine is a good idea..

Don't let a photos like this be your next post!


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## k1vsk (Jul 16, 2001)

Although it is usually sound advice (and a cliche) to not try to take a cheap approach with anything, no one has yet identified what problem(s) would occur from designing a proper substitute. The pic above is almost definitely a casting issue unrelated to failure of a (supposedly properly designed) motor mount.


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## Maine Sail (Jan 6, 2003)

*Here are a few that come to mind*

Catastrophic failure of a motor mount or the bell housing
Transmission output bearing isues
Potential transmission problems
Vibration related stress transferred to the hull
Vibration issues
Failure of the "home made mount"
Elongation of home made mounts bolt holes
Damper plate failure

The pic above was a bad casting but used more for illustrative purposes. That happened even with a factory motor mount..

I had one motor mount on a Volvo V-70 fail on my wife's car. The resulting failure took out her tranny, her exhaust manifold and down pipe and the drive shaft carrier bearing which of course is part of the drive shaft. one bad motor mount cost me close to 5k!!

Of course I never drive her car and if she had let me know it was making a funny noise I probably could have saved about 4k!! I have seen failed marine mounts destroy transmissions, shafts, cutlass bearings and shaft logs..


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## scottyt (Jul 19, 2008)

i am not saying i am doing the mounts this way. i posted with an idea, which for the most part has be shot down. i do understand the draw backs and issues with my idea, but i came for opinions.

the next ? is how do the replacement mounts that are sold like this work compared to yan mar mounts
Yanmar Torresen

scott


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## Maine Sail (Jan 6, 2003)

Funny you should ask about those mounts. I installed mounts that look identical to those that came from Hamilton Marine on a Yanmar 2Gm a few years ago. They were definitely not as plush as the Yanmar mounts and the boat at idle was like a jack hammer comparatively speaking. That being said a little more vibration than stock with a professionally designed "generic mount" is better than back yard engineering your own.

Yanmar mounts are designed to compensate for and help reduce the inherent vibration in their smaller motors..

I can't currently find them on the web site but here is a photo of the actual shelf at Hamilton in Portland where they reside. They stock three different brands and the silver ones are right there in the middle. They were not in the $60.00 range but less, and I think in the $40.00 range..


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## jjns (Jul 8, 2007)

It is a WAY better plan than trying to build your own, but you do need to be aware of the potential down side of aftermarket (A/M) parts vs original equipment (OE) parts.

1) it may not have the same usable life-span as an OE part.
2) it may have different performance characteristics than the OE part.
3) it may not be an exact fit and require some modification, labour is expensive.
4) RE & RE time is also a consideration. If it takes 10 hours to replace the part vs 10 mins, saving a couple of dollars may also be pound foolish.

Back when I 1st started pulling wrenches, dealers were the bad guy, they overcharged for their parts, ripped off their customers,blah blah blah. 
We made a habit of never using OE parts whenever/where ever possible.
I thought we were doing right by our customers. It never donned on me that replacing the same parts over and over was a result of cheap a/m parts. Then I moved into the dealer level.
Imagine my surprise when I found out that the OE parts that cost 2x as much actually lasted, on average, 10x longer. 
Added to this great discovery was that the a/m part that retailed for say $10, cost the repair shop $5. The 'same' OE part that retailed for $20 would cost $18. 
So, who was ripping off who? 'nuff said.


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## sailingdog (Mar 19, 2006)

Maine Sail said:


> I had one motor mount on a Volvo V-70 fail on my wife's car. The resulting failure took out her tranny, her exhaust manifold and down pipe and the drive shaft carrier bearing which of course is part of the drive shaft. one bad motor mount cost me close to 5k!!
> 
> Of course I never drive her car and if she had let me know it was making a funny noise I probably could have saved about 4k!! I have seen failed marine mounts destroy transmissions, shafts, cutlass bearings and shaft logs..


This is why I would drive my wife's car about once a week as a general rule.


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## Maine Sail (Jan 6, 2003)

sailingdog said:


> This is why I would drive my wife's car about once a week as a general rule.


I normally try to but I had been on one business trip after another and before I realized I had not driven her car in about 6 weeks... 5k!!

I solved this problem by prying European cars out of her fingers and buying a Honda for her! 124k = one light bulb, two $9.00 sway bar bushings, and a rear seat latch that broke. She still misses her Volvo (that was her favorite) but nothing has failed on this damn Honda!

I bring it to the dealer and I'm standing there arguing with them that they must not have looked hard enough to find something broken? I feel like they are cheating me when they send me out the door with nothing wrong and it just feels plain weird after 20+ years of owning European cars.

They think I'm nuts at Honda for wanting something to go wrong but when every trip to the Mercedes, Volvo, Audi or BMW garage was a minimum of 1k+ and every trip to Honda is a $24.95 oil change and a free wash it makes me smack my head like Homer Simpson and wonder why I ever bought a European car to begin with???

If my wife had been driving a Honda's for the last 20 years, and they had been even half as reliable as this one, the money I saved in car maintenance would have bought me my Morris... My Mercedes dealer had 35k in warranty expenses into my wife's 2000 E320 wagon with a drive line vibration. After 7 months of in and out of the shop they never could fix the problem. Got rid of that one quickly and traded it in on a All Road Audi which was even worse!!! I'm a glutton...


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