Yanmar Engine Mounts

Daverw

Daverw

Well-Known Member
Joined
2 Nov 2016
Messages
3,050
Location
Hull
Visit site
I have just had both rear av mounts fail on my 2GM20, caused by the front foot cracking. They have always appeared to be a little soft and engine moves more than I would expect and wonder if it's worth replacing them with the next up stiffness, currently Y100 on rear and fit Y150 pair. Will this make a difference? Also looking at using R&D alternatives
 
I agree that Yanmar mounts seem to allow a lot of movement but they also allow the engine to sound like a sewing machine. I did some first principles calculations on my 3YM and concluded the originals were under rated. I then replaced mine with R+D mounts and they work fine but the harder compound transmits more vibration to the hull making the engine a little louder and harsher.
 
I think you will find that comparing the cost of R&D mounts with Yanmar is an incentive to change. 4 R&D mounts for the cost of 1 Yanmar swung it for me. It will probably require a little modification, in my case the addition of spacers, to adapt to the new fixing pitch and height.
 
Daverw said:
They have always appeared to be a little soft and engine moves more than I would expect and wonder if it's worth replacing them with the next up stiffness, currently Y100 on rear and fit Y150 pair. Will this make a difference?
Click to expand...

It will probably make things worse.

If you increase the stiffness of the mounts you will increaee the natural (resonant) frequency of the system. It's a aquare root relationship, so quadrupling the stiffness doubles the natural frequency.

The rotating imbalance forces which cause the vibration are proportional to the square of the frequency, so if you increase the natural frequency by the stiffening the mounts, the imbalance forces and therefore the vibration will be larger when you pass through the natural frequency.

You see this with washing machines on "spin". They have very soft mountings for the drum so resonance happens at low speeds and the full speed spin is smooth.
 
awol said:
I think you will find that comparing the cost of R&D mounts with Yanmar is an incentive to change. 4 R&D mounts for the cost of 1 Yanmar swung it for me. It will probably require a little modification, in my case the addition of spacers, to adapt to the new fixing pitch and height.
Click to expand...

There was a previous thread that detailed which R&D mounts were the best fit replacements for 2GM20 mounts but I can't find it now. Can anyone who has done this tell me exactly which ones were best replacements for front and rear? I'm gonna do this job at the end of the season.
 
Understand about being soft absorbs the rotational vibration but they also seem to allow too much moment from the prop thrust, this is allowing the prop to push the shaft gland open. Just picked up R&D set to fit over the next two days, they seem very well engineered with casting rather than pressed steel
 
Changed them today after making spacers as recommended by R&D, updated to V100 and V150 from original V75 and V100.
Aligned shaft and run up and very pleased, noise levels seem actually better and less vibration even though harder mounts. Only a little movement on shaft which I think is a slightly worn cutlass bearing but thus can wait.
Very pleased with result and ASAP for supplying at a good price.
 
You must log in or register to reply here.

Share this page

Top