Glastron is a decent boat.
We have the same power package in the same size 2003 Chaparral. It has been mostly great so far, aside from a few issues.
Get a feeling for the boats ownership. If it appears ignored/carelessly maintained, walk away.
From our experience over several years, in addition to the above:
1) check the large 30amp(?) glass fuse in the harness from the battery to the engine and instrument/switch panel. It is in a black housing that, at least on the Chaparral, is located low and the contacts can get corroded. Contact cleaner, a brush, dielectric paste and a new fuse are your friends here.
2) check the main circuit breaker on top pf the engine, if it is original it is almost 20 years old, replace if it is questionable.
3) same for the 90amp main fuse at the starter.
4) check battery cables, they may look OK at the ends but have internal corrosion, ~$100 and some work is a great investment here
5) the 4.3 ground lug is at the back center of the engine. do yourself a favor and clean and dielectric paste this
6) you will be rebuilding carbs every few years. Thank ethanol and infrequent use. Do it at the first signs of poor running.
Also, since this is a used boat, look for the included extras. We bought ours when it was only a few years old, from the original owners, a family w/ teenage kids. I found, very well hidden, a pack of family prevention devices and a bottle of vile smelling, berry flavored, THC infused vape juice carefully velcroed behind the trim pump. Jackpot!
Enjoy, be safe, family boating is fun.