yanmar motor mount replacement idea

[scottyt]

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

[IMG][/IMG]

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

[scottyt]

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

[funsailthekeys]

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

[scottyt]

Originally Posted by funsailthekeys

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

[funsailthekeys]

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.

[captbillc]

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.

[k1vsk]

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?

[rikhall]

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

[motovationcycles]

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.

[Omatako]

Originally Posted by captbillc

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.