Re: 85 hp johnson
What year is the motor? If it's older than '73 I wouldn't buy it. Pre-73 is going to be an electric shift model that has some parts related to it that are no longer available (I bet you're getting tired of hearing that). Do a compression check. All 4 cylinders need to be within 10% of each other or it's junk. It could cost anywhere from $0 - $1000 to get it going again assuming good compression. (Worst case it needs power packs, stator, carbs rebuilt, fuel pump, etc etc). On a positive note, I had a '73 Johnson 85 that we dumped a few hundred in when we got it to get it going but it was a great motor than for the next 5 years until we sold it in great running condition. I had no issues with parts either.
An early '70s Johnson/Evinrude V4 would only be worth about $800 in good running condition so his price of $600 for an unknown is a little out of line.