Another factor, do you want to keep the boat?

If so, I would probably look around for other bids to rebuild the motor.

If not and you are planning to move to a different boat, you could probably sell-as is and not deal with the rebuild process. There is a market for people that will buy a boat in good condition with a blown motor (ie TX when they get a hard freeze). People that want to get into boating and have mechanical skills to do it themselves will save some $$.