My $30k of hull is enough to cover the owners deductible.

Do you believe that you will only be asked to pay the owner's
deductible? Why do you think the owner's insurance company won't
come after you for the money they paid to the owner?

The liability covers the rest.

Do you think your liability coverage will pay the owner's insurance
company back for the claim they paid to the owner on the hull coverage?

If I am a renter, and the engine quits because something breaks, I land
it and walk away. The insurance companies fight over who pays what.
Who are they going to get more from? Me or the others (including the
owner) who have an interest?
As it has been explained to me, inusrance companies rarely subrogate
unless they have a deep pocket or there was a blatant violation of the
regulations.
In todays litiguous society, the owner and the owners insurance company
stand an equal chance of being sued for improper maintenance.