What kind of time is 'good' really depends on how fit you are, and how much running you have done in the past.
For a club runner who's been running for a few years or more a good time would be sub 1:30, and a very good/excellent time would be sub 1:20.
For someone who has little to no history of running, and has done very few if any races of this length before a good target time would be sub 2 hours, and a very good time sub 1:45.
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Black Turtle: the most recent in a long line of users to cause my contest score some extreme embarrassment .