Most of what I'm about to write goes for all boats in general.
If there is wood in the boat, it could rot. Transoms are often rotted, even those with outboard brackets.
Have the boat surveyed, it is money well spent.
1997 250hp outboards are pretty old technology (use a lot of fuel and 2 cycle oil). They are also likely near the point that they will begin to nickel dime you to death, or worse yet blow a hole in a piston.
Use a camera or your phone with a flashlight and take lots of photos when you look at the boat, trust me you will look at them later. Take photos where your eyes cannot see (in the bilge, behind the cover plates, etc). It's kind of like looking at a new house and being able to see the framing behind the walls, gives you a better picture of how the structural integrity of the boat is.
Look for soft spots on the deck.
Tap on the entire hull with a rubber mallet, your looking for hull delamination, weak spots or cracked stringers.
Do a compression check on the engine. It doesn't tell you everything, but it gives you a starting point.
Ask lots of questions; service records, modifications, etc.
Download brochure from Grady and print the pages for the Gulfstream.
Download and print the closest performance report you can get (Grady often has old reports if you ask them). Yamaha has many, might be close enough.
Once you have the items above, you should have a feel of how the boar should perform (speed, fuel burn, maximum rpm, etc). When you go for a sea trial you should come close to the numbers. Also, you will know what the boat is supposed to look like from the factory (and what options were available).
Aslk to see and test everything, VHF radio, windshield wiper(s), tachometer, pumps, tabs, trim and tilt, lights, horn, cushions, curtains, etc. Anything that doesn't work will take your time and money to fix.
Finally, I spent many hours on a 2000 Gulfstream. Overall I liked the boat, especially the layout for fishing. However, I always thought it needed more power (it had a single 225 Yamaha EFI). I also found it frustrating how difficult it was to keep the nose down in anything above two foot seas. We installer larger trim tabs and it helped a little. I've read many times that with twins, the nose actually stays down better. I guess despite the added roughly 450 pounds on the twin bracket, the additional thrust makes the boat run parallel to the water instead or the bow constantly rising like a large beach ball that your trying to sink in a garbage can.
Sorry for the rambling, hope it helps
