Re: What makes a Mako boat good?
...What makes a used mako good?
I adjusted your question so that the answer works better. The answer: the previous owner.
When you're buying a used boat, you're buying condition. At 30 years old, that boat could be a mess or pristine depending on how well cared for it was. My boat is 40 years old, and was VERY well cared for by the P.O. The Mako can have all sorts of issues with it even if not rot, just like any boat.
Part of it might be prices in your area too. $3,500 sounds hight for that boat (unless in "like new" condition, I suppose) in my area, but NJ might be a bit higher.
Have you put it on the water, checked the floor, transom, etc.?