I'm no mechanic but here is my take on used motors either fresh or salt water..Any motor that age is a throw away regardless of who makes them in my opinion unless you have the skills that skools has and can rebuild them so you are pretty much just buying the boat. A friend of mine bought a big water duck boat last year with a very clean fresh water 1992 Zuki 2 stroke 90 HP with low hours on it and it ran like a banchie but started to heat up because it sucked up a lot of sand and the heat alarm was on at low speed so we decided to put on a new water pump...NO BIG DEAL....We worked on the lower unit for two days and could not budge it as it was fused to the power head at the other end ..He took it to a zuki dealer who even tried heat, drop weights etc but no go so the guy told him that it was toast as it would not come free ..I had a merc do the same thing a few years ago but again it was an old motor also..I have personally had MUCH better luck with Johnnyrudes over the years but thats just me and they are easy to get parts for..A friend of mine up the creek has a new VERY high dollar Zukie 300 on his whaler and loves it...I know a guy in canada that just buys old 70's and 80's johnnyrudes for his fish camps for 5 to 6 hundred dollars apiece that seem to run forever with no proper maintenance and when they blow he rebuilds them as he has so many parts available..and the winters are long....Frank