[Abull]

One of the motor mounts on my VW Pathfinder in a 37 foot Truant Sailboat is missing the rubber ring. How big of a deal is this? As far I can tell there is no excessive vibration.

 

[boatpoker]

Shaft mis-alignment, accelerated cutless bearing wear, possible transmission damage.
Unlikely but possible stuffing box and shaft log damage.

 

[svHyLyte]

One of the motor mounts on my VW Pathfinder in a 37 foot Truant Sailboat is missing the rubber ring. How big of a deal is this? As far I can tell there is no excessive vibration.

The "rubber ring", as you describe it, is a shock absorber that is, itself, supposed to carry the weight of the engine and buffer vibration/shock at it's points of support. Without, the shear pin/mounting bolt will suffer and surely fail and, undoubtedly, at the most awkward time, when you need and are working the engine hard. The mount should be replaced and the others inspected closely. If they are of the same vintage, they may need replacement as well.

FWIW...

 

[miatapaul]

Yes, I would say attend to it before taking it out. Also I would change out the timing belt if it has not been done recently. They are supposed to be changed at least every 1000 hours. If you don't know how long it has been then I would change it as they age poorly as well, sitting without running for any length of time is likely worse on the belt than hours. Not a hard job if you have good access.