Stainless and bronze impellers are good, but not necissary until the higher HP is desired, look for signs of abuse, like gelcoat worn through the bottom of the hull and rock marks all over the intake of the pump, make sure all of the controls move easily and smoothly with no "slop", grab the seats and anything else that should be bolted in hard...
If you go to look at a boat your interested in for sale, I would recommend some tools.
First and formost you need a flashlight and a mirror, you can see things even the owner does not know about, look under the engine at the mounts (do you see movement where the mount "used to be"?), look under the dash, if the wiring looks shitty, it is,, look into the intake of the pump (under the boat) if it looks like the pump has moved some gravel, it has, look inside the gas tanks and take a whiff and shine the flashlight into the tanks, if they're aluminum, you should see shiney new looking metal, if it's whitish "pass!", look at the underside of the seats, very easy to see if the wood in the seat bases is rotting, if the seat bases are rotting there is a good chance the hull construction wood is dying a slow death too.
The next tool you will bring is a small ball peen hammer and a screwdriver, just simply tap the hammer along the stringers and the floor and transom, wherever there is wood used in the construction of the hull, if the wood is good it will sound super hard, like hitting a pool table surface, if not it will sound like you struck a cardboard box use the screwdriver to lightly poke around to find how big the soft spot is, most 30-40 year old boats will have some dry rot, it's up to you to decide how bad it is.
Do not ever buy a boat in running condition without hearing it run, maybe even take it to the water if you can, this will bite you in the ass every time.
Lastly if you buy a turn key boat, go through everything service wise and take it to the water as soon as humanly possible, recheck the oils and whatnot, if something does not sound right, it isn't.
If its sounds too good to be true... well you know the rest.
Good hunting!
GT
