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Discussion Starter · #1 ·
I am looking at replacing the engine mounts in my 1978 Beneteau First 30 this spring. The engine is a Yanmar YSB8.
What am I looking for in a replacement mount? compatible hole patterns, post height rubber thickness? Are these things more or less readily available or are they very part-number specific items?

It's my first boat and my first spring-commissioning so I can use all the help I can get!

Cheers,

/Jason
 

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:eek: :eek: :eek:
OMG!
:eek: :eek: :eek:

If you don't want your boat to sink or your motor to break or the space shuttle to blow up you had better use new stock motor mounts.

You might even be killed!:laugher :laugher :laugher :laugher

I am looking at replacing the engine mounts in my 1978 Beneteau First 30 this spring. The engine is a Yanmar YSB8.
What am I looking for in a replacement mount? compatible hole patterns, post height rubber thickness? Are these things more or less readily available or are they very part-number specific items?

It's my first boat and my first spring-commissioning so I can use all the help I can get!

Cheers,

/Jason
 

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Discussion Starter · #5 ·
Ok, good reading :) No, I am not planning on makign my own mounts. It was more a question of using what is readily available versus finding an exact part number with limited availability and ordering online with shipping and customs brokerage fees. But from the tail end of that thread, it looks like if I can match the hole-pattern on the mounts to the ones in the strings and choose a mount with a properly sized bolt for the engine then all should be good...

And judging by the reaction to Scotty's DIY idea, I won't begin to mention my plan for my boat's instrumentation! :laugher

Thanks for the info.

Cheers,

/Jason
 

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I have finished my research.

After interviewing paid mechanics who's experience adds up to over 300 years I have come to these conclusions.

The motor mount bolts do not break.

The steel parts in motor mounts do not break.

The rubber to steel bond does not break.

The culprit--- the rubber. It rips apart from the engine pulling it apart.

The OP original mount shows nothing but rubber and glue holding the two metal parts together.

Scottyt wanted to save money by modifying his mounts with rubber and through bolts and I agreed but others disagreed, some even thought he might be killed.

Someone mentioned the failure of the rubber seal on the Challenger space shuttle as an example--only the rubber fails on a motor mount.

Someone mentioned the science that goes into the rubber of the mount---only the rubber fails on a motor mount.

Someone mentioned automotive accidents where the motor did not come loose. Most automotive motor mounts are designed to be captive, then cannot come completely apart. I say most because some are now relying on just rubber (cheaper).

Someone mentioned something about a bolt not having any strength unless it was pulled down tight. I guess these super strong bolts I use are just butter until I tighten them??

Someone scoffed at my idea of using a truck mud flap made of conveyor belting although this material has multi layers of material and rubber and is easier to come by as a mud flap than getting an industrial supplier to cut you some off a large roll.

The CRACK picture. What a scare unless you noticed the washer mark on the engine that shows that the mount bolt should have gone through the middle hole. I hope that was not and example of the poster work when he was young working in a boat yard.

Let's just take a breath here and do a little SWAG.

A one cylinder diesel engine with transmission and accessories weighs in at 200 pounds and a four cylinder at 800 pounds. I going to guess that 70% of this weight is above the center line of the crankshaft where the mounts should be.

So there you have it, a lump of cast iron held in place by 4 rubber mounts and one solid mount, the output shaft connected to the prop shaft. All is well and good in the static world.

Now think what would happen if the two rubber mounts on the torque side were ripped and you did not know it and you had to power through fifteen foot waves...Rockin' and rollin' with that lump of cast iron just waiting to come loose and the only thing holding it any way near where it belongs is old rubber.

Powering, heck, what would happen if you were sailing and got knocked down or rolled or pitch poled!

Be vary, vary afraid.

Remember that the thing that breaks is the rubber.

Personally I would want at least one through bolt in each mount to guarantee that my motor would be kept in it's proper place but hell that is just me.:rolleyes:
 

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Wow..

The CRACK picture. What a scare unless you noticed the washer mark on the engine that shows that the mount bolt should have gone through the middle hole. I hope that was not and example of the poster work when he was young working in a boat yard.
Bandit,

With all due respect please do not take me out of context and insult your intelligence by doing so.

What a scare unless you noticed the washer mark on the engine that shows that the mount bolt should have gone through the middle hole.
First it was NOT a scare but an illustration to show what a potential outcome of home made motor mounts might look like. MIGHT look like...

The part about the washer hole is a 100% bold faced lie with NO factual backing. The FACT is that Westerbeke puts three holes in that bell housing for the express purpose of mating up to various width engine beds. ANY of the three holes can be used and the bell housing is designed for load with all three holes loads in mind. Your statement is 100% false and makes you look....well... I'll be polite....

As I CLARIFIED in post #26 & that image, and bell housing, failed due to a bad casting and was used only as an illustration. If you had actually read the thread and posts, as opposed to vilifying others, you would have seen that...... I quoted myself below..

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


This casting absolutely, positively, 150% DID NOT fail due to the hole the motor mount was in so please stop shooting from the hip with your incorrect and absurd "facts".

Westerbeke was kind enough to send me a brand new bell housing at 2870+ engine hours because it was a poor casting and an original factory defect. They did this because they are a good company. I never asked them for this only to examine the bell housing and give guidance as to what may have caused this after 2870+ hours.

Clearly you need to step it up in the research department before spouting off at other members or accusing me of a bad installation or using the wrong hole in the bell housing.

I have installed quite a few motors and also a fair number of after market & OEM motor mounts. In some instances, especially with Yanmar's, the owners are not as happy with the after market mounts. I have also switched one boat back to factory after going to non-factory and it happened to be a Yanmar. The OEM mounts are specifically chosen for these engines for a reason. The Westerbeke mounts in particular are quite well engineered.

You are also quickly forgetting that I steered the op to a source for after market mounts that would perhaps cost him less than his DIY idea or damn close, and I was one of the only ones to do so in that thread.

Aftermarket mounts are fine and they can save you money but you may not like the vibration nor find an exact match, bolt pattern wise, to the factory Yanmar mounts.

I have yet to find an after market mount that works as well at reducing vibration, on Yanmar's, as the factory Yanmar mounts do. If you happen to find some please let us know what they were.

Seeing as you have been of little help to the OP, other than to spread untruths and take folks out of context, I will try to help.

This is the motor mount section at Hamilton Marine:


They stock three different brands of after market motor mounts.

Here are a few links that may get you started on your search.

Hamilton Marine Motor Mounts (LINK)


AV Products (LINK)

Globe Ever Stay Mounts (LINK)


The Evolution Company Mounts (LINK)


Having had direct experience with the OP's exact question I highly recommend the factory Yanmar mounts if you can afford it.
 

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Timebandit—

IMHO, it would be much better if you didn't attack one of the more respected members of this forum who has generously spent time and effort in putting together some of the best documented DIY instructions on the web for sailors. Maine Sail does know what he is talking about, in some cases far more so than the "professionals" in the marine industry that I've seen.
 

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I would suggest using the original Yanmar mounts, if however you require an aftermarket mount, R&D make a range of mounts, including mounts for Yanmars with Yanmar spec'd mounting holes. In the USa they are available through PYI Inc. Max-Prop PSS Shaft Seal Seaview Radar Mounts R&D
When we bought our boat last year, it had a brand-new 3YM30 mounted on PYI mounts. One of the mounts had failed. The engine had 4 hours on it, and I believe it had never left the dock, so vibration was not the cause. As for time - the boat had been sitting for less than a year.

The problem is, Yanmar mounts are very tall. If you have a clearance problem, it's awfully tempting to use aftermarket mounts instead of rebuilding the beds.

Is it possible that Poly Flex or some other company might use more sophisticated materials to get the same results (the perfect blend of soft and stiff) that Yanmar mounts get with height?
 

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This mount design will keep the motor where it belongs when the sh!t hits the fan.

Anything else is ---

Last post on this subject.
 

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Does that mean your last post on this subject, or you want the rest of us to cease and desist, too? I'd say the topic of engine mounts is always open to discussion, at least until I figure out why mine failed without actually being used.
 

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Naw

Just my last post on a better motor mount.

What failed on your motor mount and do you have it?

It could be that it is the the first one tightened and then the motor was twisted or moved fore and aft or side to side. This would induce a tearing motion even with out the motor running. If you still have it, try putting the pieces together (the rubber will kinna interlock) to see what it looked like before it failed, it will give you a clue.





Does that mean your last post on this subject, or you want the rest of us to cease and desist, too? I'd say the topic of engine mounts is always open to discussion, at least until I figure out why mine failed without actually being used.
 

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With..


This mount design will keep the motor where it belongs when the sh!t hits the fan.

Anything else is ---

Last post on this subject.

I know this is your last post but..

With the hundreds of thousands of sailing posts on the many sailing forums you'd think you'd hear of this problem, where the motor breaks free and flails around. I can't recall reading about an engine falling out of its mounts? Can you point us to some discussion on this inherent problem?

I have been in four separate knockdown incidents, in rough conditions, in my life (this is not counting spinnaker broaches while racing). In not a single one of them did the motor tear free or even break a mount. In one storm we were knocked flat three times, and to the spreader too many times to count, and other than cabinet latches failing and pots, pans and other assorted things breaking free the motor stayed put.
 

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Let's just take a breath here and do a little SWAG.

A one cylinder diesel engine with transmission and accessories weighs in at 200 pounds and a four cylinder at 800 pounds. I going to guess that 70% of this weight is above the center line of the crankshaft where the mounts should be.

So there you have it, a lump of cast iron held in place by 4 rubber mounts and one solid mount, the output shaft connected to the prop shaft. All is well and good in the static world.

Now think what would happen if the two rubber mounts on the torque side were ripped and you did not know it and you had to power through fifteen foot waves...Rockin' and rollin' with that lump of cast iron just waiting to come loose and the only thing holding it any way near where it belongs is old rubber.

Powering, heck, what would happen if you were sailing and got knocked down or rolled or pitch poled!

Be vary, vary afraid.

Remember that the thing that breaks is the rubber.

Personally I would want at least one through bolt in each mount to guarantee that my motor would be kept in it's proper place but hell that is just me.:rolleyes:
Just an update to this very old thread. I installed a new blade for my band saw today and wanted to try it out. In the trash can was a Westerbeke factory mount. I decided to do a little cut-a-way...

No through bolts but they are fully rubber isolated / dampened and captive.... If you break one of these you have waaaaay more to worry about...;)

Sorry for the tardy update...;):D


 

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..and apparently the new blade works just fine!! ;)
 
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