Bob is spot on, if youre not too boat savvy, bring someone who is. Go run the boat, not a trip around the marina and back, but go burn half a tank and run it HARD. Im not saying try and break it, but expose any weaknesses. flip every switch, push every button, jiggle every wire you see, then repeat.
take a GOOD look at the flippin trailer!! A broken axle or fried bearing before your first trip out will pi$$ you off like you wouldn't believe possible,
So what kinda boat are you looking at getting anyhow?