Hi...its a difficult situation to make comment on or judge, just depending on assumptions, experience or even cynical thoughts.
The latter thinking, might agree with the above (and usually correct) thinking.
First thing to mind from what you've mentioned might be around the evidence of the engine running, but the suggestion that it needs a simple addition of a battery cable to make good. How did the guy get it running ? Assumption might be that he might have used such a cable to do this...so why would such a thing not be included in the deal ? a little strange otherwise.
Another thought might be that I know that even the most worn of outboard engines will run and sound revvy and quite healthy, when running in a guys driveway on a set of muffs and not under load. she could even be only firing on half her cylinders and apparently sound half decent to the unaware. Put her in the water and under load...different story.
With regards to the boat herself, unless there has been some intervening surgical work or restoration to her stringers, floor and transom in her lifetime, the chances that such things are in good health otherwise are almost next to none.
All that said and done, you never know though. There are genuine lovely and pampered boats of similar age in existence. But I might suspect that those boats that fall into this rare category might not be often feature the mention or requirement of a battery cable.
Anyway...if you are still keen, long story short, make sure you do a compression test on the engine, make sure she has a healthy gearbox, ignition and charging ability too. Check the trailer is actually designed for a boat and in good health. And certainly make sure the transom and stringers are healthy. Otherwise you will be quick to learn a harsh and unfortunate lesson on elderly boats.
Best of luck
