sounds like the mounts are shot based on your description.
it can be quite a large job to fix this depending on the age of the motor and if any corrosion has set it (i.e snapping bolts)
if you are handy with a spanner then i would do it myself, if not you'll be spending quite a lot on labour unfortunately.
you should start by getting a service manual, some searching with your model year and or serial may get you a free one looking on google.
EDIT- this may give you an idea.
i would think you need No 46, 47, 48, 49, 51 (2 of), 66 and 72 (2 of) at a quick glance and that is hoping no bolts break off.
please note, the above is only for a yam 55, i don't know what age you have so i only got it for explanation purposes.
hope that helps.