Replaced Motor Mounts

[Sailgunner]

Replaced the motor mounts on my 23 yr old 410. Purchased Ellebogen mounts which were a direct replacement. The job turned out to be not too bad.

Originally I thought I would remove the motor mount brackets from the engine and remount the new engine mounts off the boat. As it turned out I could not remove the bracket bolts from the engine. So instead I was able to raise the engine high enough to remove the old engine mounts. I purchased a 1 ton chain hoist and used a 4x4 across the cabin top to raise the engine.

I did this project while the boat was in the water and I have a dripless seal so I had to be careful with that.

After removing the bolts from the engine coupling and raising the engine at the forward lifting lug I was able to move the engine forward about an inch to get it off the shaft coupling. I raised the rear of the engine with the rear lifting lug and put a block under the transmission.

From there it was a matter of raising the engine, replace rear mounts, lower the engine. Raise front of the engine, replace fronts mounts and lower the engine.

Then we was gently lowered the engine while moving it back to the couple. One minor engine mount adjustment and everything lined up.

The job took about 4 hours with the help of my wife. Send me a PM if you have any questions.

 

[Hayden Watson]

I did them on my C30 with about the same procedure except that one of the old bolts was seized into its hole. It took me about a week of daily cycles of heat-heat, squirt-squirt, tap-tap to finally get it free. It made a big difference in the vibration in the boat. The old mounts were as hard as steel and did nothing to absorb the engine movement.

 

[Ralph Johnstone]

And how did the shaft alignment go after replacing the mounts ?

 

[Hayden Watson]

Just like every other alignment. I started by getting the height and went to horizontal alignment and then started to work on the angle. I went through each of those steps probably 3 times until I was satisfied. I ended up with it less than the recommended 3-thousanths.

 

[Ralph Johnstone]

I ended up with it less than the recommended 3-thousanths.

Lots of cursing and swearing there.
The only saving grace after my first alignment job ( 0.010" angular error from the factory ) after getting the boat new, was that it took years for the error to go from 0.002" to 0.003". I did eventually get around to getting the 4" flanges back to 0.002" with much cursing and swearing. Just not the kind of job I'd like to do on a regular basis.

 

[Rick D]

So you obviously researched this. I am curious how the Ellebogen mounts compare to the OEM Yanmar mounts. Specifically, I have read that the Yanmar mounts have differing compression values to sync with the engine's shake pattern. Do the Ellebogen mounts? They look like an attractive alternative.

 

[Sailgunner]

So you obviously researched this. I am curious how the Ellebogen mounts compare to the OEM Yanmar mounts. Specifically, I have read that the Yanmar mounts have differing compression values to sync with the engine's shake pattern. Do the Ellebogen mounts? They look like an attractive alternative.

They are fine at the dock. Can't do a sea trial for a while but I doubt there will be any problem.

 

[Tally Ho]

Replaced the motor mounts on my 23 yr old 410. Purchased Ellebogen mounts which were a direct replacement. The job turned out to be not too bad.

Originally I thought I would remove the motor mount brackets from the engine and remount the new engine mounts off the boat. As it turned out I could not remove the bracket bolts from the engine. So instead I was able to raise the engine high enough to remove the old engine mounts. I purchased a 1 ton chain hoist and used a 4x4 across the cabin top to raise the engine.

I did this project while the boat was in the water and I have a dripless seal so I had to be careful with that.

After removing the bolts from the engine coupling and raising the engine at the forward lifting lug I was able to move the engine forward about an inch to get it off the shaft coupling. I raised the rear of the engine with the rear lifting lug and put a block under the transmission.

From there it was a matter of raising the engine, replace rear mounts, lower the engine. Raise front of the engine, replace fronts mounts and lower the engine.

Then we was gently lowered the engine while moving it back to the couple. One minor engine mount adjustment and everything lined up.

The job took about 4 hours with the help of my wife. Send me a PM if you have any questions.

@Sailgunner,
I am curious if you chose mounts because they were cheaper than OEM, or somehow better than the Yanmar mounts?

I will have to replace mounts at some point in the future, and would like to understand what you have learne.

Thanks,

Greg

 

[Ralph Johnstone]

They are fine at the dock.

What more could you ask for ?

 

[Ralph Johnstone]

I will have to replace mounts at some point in the future, and would like to understand what you have learne.

Greg, if you have Yanmar mounts, keep an eye on them for clearance :

I was forced to replace one due to leakage of sea water and diesel fuel on it for some time. Looked like an interesting job so replaced it one winter. This shows measuring the height, as removed, in order to set up the new mount for installation.

The other three mounts are 24 YO and the replaced one 20 YO. All still show 3/8"± loaded and no problems with vibration. I think they may last the life of the boat if protected from fuel leaks.

 

[Hayden Watson]

The elevation is one of the signs that the motor mount needs replacing but the biggest reason is that they cease to perform their primary function. If engine location was the primary function, it would be much better to bolt the engine to a strong engine bed with a steel-to-steel connection. For an internal combustion engine, that is not the primary function of the motor mount. Its purpose is to isolate the engine vibrations from the frame of the thing it is mounted into. Motor mounts most often fail by getting too stiff to perform this isolation function. The nature of rubber is that it suffers from work and age hardening. Over time the mount continually gets harder and stiffer so that it no longer can isolate the vibrations. To check for this, push and pull on the top of your engine and see if the mounts will flex. If you see no movement, they have failed to do what they are meant to do.

 

[Tally Ho]

Greg, if you have Yanmar mounts, keep an eye on them for clearance :

View attachment 212262

I was forced to replace one due to leakage of sea water and diesel fuel on it for some time. Looked like an interesting job so replaced it one winter. This shows measuring the height, as removed, in order to set up the new mount for installation.

The other three mounts are 24 YO and the replaced one 20 YO. All still show 3/8"± loaded and no problems with vibration. I think they may last the life of the boat if protected from fuel leaks.

Thanks Ralph,

I will measure them sometime this winter. They look OK (no oil or diesel spills on them,), but they are probably 34 years old. I have never found receipts or maintenance log entry to suggest a PO replaced them (I have owned the boat for the past 8 years or so of its 34 year life .

To @Haydon walker’s point, I assume if the rubber is shot (or weak), it would manifest itself in smaller clearance as the rubber squishes more and more.

Good knowledge.

Thanks to both of you.

Greg

 

[Hayden Watson]

To @Haydon walker’s point, I assume if the rubber is shot (or weak), it would manifest itself in smaller clearance as the rubber squishes more and more.
Greg

Not necessarily true. When I replaced the 34-year-old motor mounts in my 88-C30 they still measured to the original dimensions, but they might as well have been made out of solid steel because there was no movement in them whatsoever. I have never seen one get squishy. They get hard.

 

[Tally Ho]

Not necessarily true. When I replaced the 34-year-old motor mounts in my 88-C30 they still measured to the original dimensions, but they might as well have been made out of solid steel because there was no movement in them whatsoever. I have never seen one get squishy. They get hard.

Ahhh. Ok. Good to know.

I thought oil/diesel contamination would make the rubber soft.

When My engine is at a low idle, it bounces around a bit, so I am guessing mine didn’t get too hard yet.
around 6:0 in this video, I have the engine started and in gear…you can see a little movement of the shaft, etc.

When running above a low idle she sits pretty still…

Greg

 

[Hayden Watson]

It is nomal for the movement to be less at higher rpms. The best way that I have found to check the daping of each motor mount is to place my hand on the mount so that part is on the fixed base and part on the moving engine side. You should feel a difference between the movement in the two parts. You can also push and pull sideways on the top of the engine when it is shut off and see if the mounts flex.
In normal practice, your mounts should not be exposed to diesel or oil. If it is, you have a leak that needs to be repaired.

 

[Ralph Johnstone]

When My engine is at a low idle, it bounces around a bit, so I am guessing mine didn’t get too hard yet.

I see the same thing with mine at 800 RPM and steadies out somewhere near 1500 RPM. Pretty sure the two cylinders are swapping pistons at 800 RPM .

When I replaced the 34-year-old motor mounts in my 88-C30 they still measured to the original dimensions, but they might as well have been made out of solid steel because there was no movement in them whatsoever.

Do you have a Yanmar or is it a Universal seeing as the boat is a Catalina ?

To check for this, push and pull on the top of your engine and see if the mounts will flex. If you see no movement, they have failed to do what they are meant to do.

You got me to thinking there and let me tell you, it's a painful process in this cold weather. I was just out to the boat this afternoon cleaning up the mess after inspecting the HDI SS mixing elbow. I remembered your comment about moving the engine on the mounts to see if the mounts were still soft. Of course, the engine sits as solid as the rock of Gibraltar because the shaft holds it rigid. However, the last time I did a shaft alignment check about 5 years ago, the engine moved around like a jolly jumper when disconnected from the shaft. This was the same amount of flex as my first alignment job 2 years after getting the boat from the factory (22 years ago). Vertical and horizontal alignment are just a feel around the two flanges to see if they're close. Incidentally, the two flanges are also slightly different diameters so hor. and vert. alignment is pretty much a guess at best. While disconnected, leaning against the engine is enough to knock these two alignments into left field although they do return to their original position when the leaner gets off the engine. It's all about angular alignment.

 

[Hayden Watson]

Do you have a Yanmar or is it a Universal seeing as the boat is a Catalina ?

...Of course, the engine sits as solid as the rock of Gibraltar because the shaft holds it rigid.

mine is a Catalina with the Universal M-25XP.
The motor mounts are made to have different strength in the three primary directions. The softest of these is transverse horizontal. This allows the engine to rotate about its crankshaft which is the way that the vibrations primarily come from in the engine.

 

[Ralph Johnstone]

mine is a Catalina with the Universal M-25XP.

There is a difference between our motor mounts both in mechanical design as well as material selection which may well be causing the difference in performance and longevity. Do you have a picture of an original mount available ?

 

[Hayden Watson]

Personally, I do not care what design, style or manufacturer the mount is. The function is the same on all of them and the differences are in style to avoid patent infringement. Here are photos of the OEM and the Vetus K50 that I used. The important thing is that the actual working load on the mount is between the min and max load ratings for the mount. This concept of working load is the part that is most often misunderstood. It is the static weight of the engine (usually total weight / number of mounts but may vary) plus and minus the load due to the max torque of the engine. You find this load by taking the rated torque of the engine and deviding it by the transverse distance between the mounts. This might be the same front and rear or different. This is the reason why some engines have different mounts on port and starboard.
It is important to have the load on the mount that is inside the min/max rating of the mount because they are springs. If you use a spring that is too stiff it will not deflect. if it is too soft, it will bottom out and not deflect. In both cases the mount will not serve its perpose of abosorbing vibrations of the engine.