Re: 1993 pontoon boat
Probably a Sundancer. They are still in business. Don't know a whole lot about them, but given its age I suspect it will have foam filled toons. If so, I would pass. Also, that sounds like too much motor on an eighteen footer, so I'd ask the seller pointed questions about the motor. Obviously it's a repower, but you need to know the story. Also, 18' is pretty small. It may be plenty for you, but if you have a couple of kids I doubt it. Regarding what to check in general though:
1. Shake the front of the barge then quickly put your head close to the toons to listen for sloshing, but note that if there are leaks you wouldn't necessarily hear the water if the toons are foam filled.
2. Check the motor pod for cracks or other signs of trouble.
3. Check compression on the motor of course.
4. Turn the steering wheel as though you were driving. An unusual amount of slop of stiffness could be a sign of trouble.
5. Turn on all switches, stereo, etc.
6. Poke your head under the helm and look at all the wiring. A rat's nest of wires is an indication the boat has been subjected to bubba mods.
7. Run your hand along the upholstery. It should feel thick and soft. If it feels dry and brittle it won't be long until new vinyl time.
9. Take a good look underneath the boat. Look for bent or beat up pieces, missing bolts, etc.
10. If possible, jack up the trailer and spin the tires while listening closely for bearing noise.
11. Check the trailer lights.
12. Check the trailer frame for rust, cracks, etc. and the bunks for rot or general degradation.
13. Water test extensively.
There's a really good thread from some time last year about what to look for if you want to read more. Good luck.
