My thoughts are that boating on the ultra cheap usually yields disappointment. If you have a running 18hp merc at the moment, and a serviceable used 16 foot tin boat, then I’d be saving my money for a newer 30hp 4 stroke Honda or Suzuki. There is not a whole lot that can go wrong with a 16 foot tinner. If the transom goes, you can generally replace it quite easily if your handy. A small leak? Tip it over and get a buddy to help you bang some rivets tight. Flooring shot? Rip it out and replace. It the boats in decent shape it will last you for years. The motors have a finite lifespan. And while that old Johnny may run well, it will break down eventually or as someone else said, it’ll smoke like mad. If you buy once and cry once on a newer motor, you’ll be on the water trouble free for years.