MD3 Volvo Motor Mounts

Hello everyone. I am finishing up my preparations for heading out to live aboard. My last serious issue is relating to the motor mounts. Take a looks at the mounts themselves. There is a stud that appears to be welded to the engine bed with a round rubber bushing with a hole in the center. The mounts as you can see are badly worn and in the rear provide no dampening. I have been to every marine store/surplus/boat yard and no one seems to recognize them. I need a solution sooner than later. I have read that there are two mounting types, "Hard" or "Flexible" These mounts appear to be hard. I would attribute the badly worn cutlass bearing that I replaced on the last haul out after my purchase of Hannah to the vibration caused under power as the engine vibrates transmitting that through the prop shaft and log to the bearing. Any and all advise would be greatly appreciated. I have thought about making my own from urethane bushings or auto body mounts and as a last resort using a hockey puck shaved to be in trans prop flange tolerance with a hole drilled in the middle in the mean time to finding a solution. Thanks in advance!

I know they are dirty, I'm cleaning out the engine bay next, just replaced the transmission and sealed the valve cover oil leaks.

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Motor mounts are always a trade-off between freedom of movement and transmission of vibration.
If your drive train has a universal joint on a splined shaft and a separate thrust bearing, you can use soft, circular silent blocs like the ones used for auxiliary generators or industrial purposes. During starting and stopping the diesel diesel will rock, jump and swing, but noise and vibration are not transmitted to the hull.

With a rigid drive train you need the square motor mounts that contain a solid block of reinforced rubber. They allow no visible engine movement and absorb only part of the vibration, but protect the drive train against unacceptable loads. If there is no thrust bearing, the engine mounts have to take up the thrust as well, that is why their length is more than twice the width.

 

engine mounts

the mounts appear to be rubber donuts placed over fixed bolts that the engine mount flanges sit on. No way other than donut thickness to adjust the engine alignment. I would think you need something soft enough to absorb some of the engine vibrations, yet hard enough to keep the mounting nuts from loosening. Trial and error custom design. If you have room, a flexible coupling between the output flange and the shaft will help ease some of the alignment issues. Engine vibs don't usually effect the cutlass bearing. Bent shaft or un balanced prop are the usual culprits.

 

Those are pretty poor mounts and maybe home made. You would be better off replacing them with proper marine mounts if you can find similar height size so as not to require major engine mount plate modification. Even so it would be worth it.

A bolt through a steel plate with a rubber or not is not a proper mount.

Same with your idea of a rubber cush drive on the shaft , if the bolts go right through it is not flexible. You have to bolt the cush to the drive and the cush is bolted to the engine.

It would'nt be expensive to get this right expecially as you can now move the engine forward when fitting new mounts and give some space to get the cush drive in.

You may have to move it forward any way to get some better mounts in. What is your shaft angle?

 

Thanks for all of the input! After looking at all the options and then my wallet I decided to make a temporary solution for 4.99 and about 2 hours time. I will replace the mounts with a proper setup when I can afford it. Here is what I did in the meantime.

I went to my local hardware store and purchased the 3 hardest rubber mallets I could find. Got my calipers out, feeler gauges, hacksaw, 24mm deep socket with 3ft extension, breaker bar and my smallest jack. I unbolted the transmission from the prop shaft. Then lifted up the engine and removed the old mounts. Then measured lowered the engine until I could not fit my smallest feeler gauge between any part of the shaft mount and trans flange. I then measured the distance between the motor mount and base of the stud. Then I took that measurement and added 3mm and transposed that onto a rubber mallet cutting it with a hacksaw to make a "puck." Then I drilled the puck with a wood butterfly bit the diameter of the stud. I re measured all sides of the puck and if it was off sanded it to the correct diameter. Then pushed the puck onto the stud and repeated the process for the others. After lowering the engine back down it was sitting about 2mm high. Using the break bar I could tighten the stud bolts to take up the exact distance I needed. The end result was no gap at all between the trans flange and prop shaft. I ran the engine for 30 min and re tested the gap to find no gap. The next day I motored off to my new slip 15 nautical miles at 2500 rpms with little to no vibration thought the boat where as before it was quite noticeable. At the slip I re tested to find no gap again.

For the meantime. a $5.00 solution to my problem will do until I can get proper mounts. I figure the boat has had this setup for the last 36 years and even if I have to change mounts each season the time spent making mounts is well worth the expense.

Any thoughts?

 

Forgot the pictures http://img15.imageshack.us/slideshow/player.php?id=img15/6002/12354555607bi.smil

 

Good job, I like your attitude.
Make a note to replace the mounts again in 2045!