3GM30F Engine Mounts

[Attikos]

Originally Posted by RickyEM

My mechanic said something about putting 1-2 fingers underneath, rather not being able to, so I think it has to do with how flattened they are?

I'm assuming that's fingers beneath the mounts, in the gap between its top and bottom halves. I'd think that when it compresses that much the lower edges of the steel cup covering the top are striking, or about to, the flat parts of the steel plate on the bottom. Does that meet your understanding of it?

That would make sense. Rubber under stress does deform in time, and once those mounts sag enough not only would they fail to absorb vibration well, the propeller shaft would be slipping out of alignment.

I wonder how many years it typically takes these Yanmar mounts to do that? Anyone have a feel for it?

[wsmurdoch]

These images are from the Chilton's manual.

[Attikos]

wsmurdoch, now you're talkin'! A gap of 3/16" or less or two years of service whichever comes first is an idea I can work with.

Much as I hate to spend Yanmar's exorbitant charge for new motor mounts, it's not as bad as damage to the shaft, stuffing box, bearings or gearbox. Maybe there's a less costly substitute, too. Worth looking for, anyway.

[jimbunyard]

I would never pay 150.00 for a mount that isn't even fail safe. Even the pricey Polyflex mounts are less than the Yanmar ones and they're failsafe designed. You can get perfectly adequate mounts of varying durometers in the US for as little as 40-50.00, and probably cheaper. I'm guessing the 50 is the durometer rating for the rear and 100 is the rating for the front; a call to a knowledgeable specialist should help in determining if this is in fact true.

[Training Wheels]

Everybody who changes their engine mounts every 2 years please raise your hands.

What, I don’t see any hands!

Seriously, anybody know of an aftermarket replacement?

[RickyEM]

Originally Posted by wsmurdoch

...After the book appears, I click on the pages of the book, choose "save as" and save it on my PC.

Bill

It was the right click and download I was not doing

[wsmurdoch]

Originally Posted by jimbunyard

I'm guessing the 50 is the durometer rating for the rear and 100 is the rating for the front; a call to a knowledgeable specialist should help in determining if this is in fact true.

I have been told that the number on the mounts is the weight in pounds that each mount is designed to support. (But, I also find it odd that a Japanese company would use pounds. So.... whatever.)

I have replaced the four engine mounts under my 3HM35F three times in the 14 years I have owned the boat. First, a year after purchase when I found the ticking noise the surveyor could hear but could not locate; the forward port bolt was broken at the top of the mount. Second, as a preventative when the engine was removed, rebuilt, and reinstalled. And third, last fall when the forward port mount had collapsed to the point that metal was hitting metal when heeled to port or in rough seas; I then on Mac Boring's advice went from 4x100 mounts (124772-08341) to 4x150 mounts (121370-0835) because a non-Yanmar alternator and a refrigeration compressor are mounted on my engine increasing its weight, and the mounts are not attached to the engine/clutch in the factory locations. Anyway, the lifespan in my case seems to be 6 or 7 years.

Bill

[Wotname]

Originally Posted by Training Wheels

......

Seriously, anybody know of an aftermarket replacement?

Polyflex.

These are popular in Australia and are exported worldwide. I don't know if they are price completive but they have a good reputation. They will support an engine upside down and the flexible component can be replaced without replacing the entire mount.

The Y series are designed as Yanmar replacements and I know of some Yanmar dealers who fit them as standard in lieu of the Yanmar mounts.

Poly Flex Group - Advanced Polymer Technology for Vibration Control - Y Series

Their website is a bit clunky

[Badsanta]

http://www.pyiinc.com/
I got mine from these guys. I have not installed as yet. But look great.

[Attikos]

The hardness of rubber is measured on the Shore A scale, which tops out at 100, or zero compressibility as detected by the plunger instrument used to test it. No motor mount would have a Shore A rating of 100; that would provide no vibration absorption. The explanation of rated weight per mount makes more sense, but don't take my word for that.

In cars, a common motor mount lifespan is five years or more. Some last the life of the car. I'd think it would be somewhat less for shaky marine diesels.

[Alan Mighty]

Originally Posted by Attikos

The hardness of rubber is measured on the Shore A scale, which tops out at 100, or zero compressibility as detected by the plunger instrument used to test it. No motor mount would have a Shore A rating of 100; that would provide no vibration absorption. The explanation of rated weight per mount makes more sense, but don't take my word for that.

The Poly Flex mounts for a Yanmar 3GM30F do seem to come in different Shore A Durometer Hardness ratings. Poly Flex signals the Shore A Durometer Hardness of a mount by the colour of the polymer: scarlet for 90; cyan for 95; and so on.

Compare the two Poly Flex mounts for a Yanmar 3GM30F:

Y#2CTF: Poly Flex Group - Advanced Polymer Technology for Vibration Control - Y#2CTF Mount
Y#2.5CTF: Poly Flex Group - Advanced Polymer Technology for Vibration Control - Y#2.5CTF Mount

The R&D Marine mounts marketed by PYI Inc seem not to distinguish between fore and aft (although recognising that Yanmar does specify fore mounts and aft mounts). See R&D Marine Mounts.gif, about 71 KB

[Attikos]

Good info there, Alan Mighty.

[RickyEM]

Can you tell if the height of the mounts is the same, so that the alignment will be unchanged?

[Alan Mighty]

Originally Posted by RickyEM

Can you tell if the height of the mounts is the same, so that the alignment will be unchanged?

Have a Captain Cook at the URLs for Poly Flex and the graphic for R&D Marine that I posted above.

Poly Flex quotes a minimum height of 101 mm (3.976 inches).

R&D Marine quotes a minimum height of 3.94 inches.

And of course alignment need to be checked and adjusted, as always. New polymer will take time to compress to what one hopes is something stable.