I think folks here, including you Gene, are forgetting the main point. We
are talking about the umbrella (general liability insurance extending past
the upper limits of the main policy), not the main policy itself on the cars
or boat. If damage is done to the the car or boat by a 3rd party driving
them, the main policy will cover the damages if the 3rd party is not
insured. If however, that 3rd party kills someone while driving the car or
boat *they * will be responsible for all claims against them, not the owner
of the vehicle and actual insured.
Why should the insurance company extend *liability* coverage to a 3rd party?