That GT 160 hull wants a "tower of power" Merc! We have ran numerous older 70s 80s mercurys with zero issues, I am partial to the two strokes, lighter, torwue, less moving parts, etc. but like you mentioned when problems do occur its becoming harder to find shops to work on them. But usually with them they arnt horribly hard to figure out. Very odd someone cant track down whats going on with your evinrude.
If it were me, I would stick with a two stroke, the question you would have to ask yourself is if you want a motor with oil injection or pre oil injection. Some of the early injection models can be hit or miss, some run perfectly for years, some fail and blow the powerhead. No matter what a used motor is a gamble, for example my uncle has a 2011 150 Merc optimax the fancy air compressor failed this summer, loosing them a month on the water and 1500 dollars in repairs later. I find myself more comfortable with an older two stroke because overall there is just less going on and can be easier to diagnose. If you know your way around motors, older two strokes arnt hard to keep operating, if you dont have as much experience, then a newer one may put your mind at ease. All depends on your budget as well.
Good Luck, I am interested to know your decision.
