The OX66 line was very reliable. If they were broken in properly, maintained properly, propped and used properly throughout their life, they probably still are. However, one thing to think about is that they are now 10 years old. And with age, you also may want to look at other things like corrosion.
Decide on what are you planning to do with the boat. I'm assuming the models you are looking at are in the 25' line with a deep v. Most of the 25 Deep Vs have a 173 gallon fuel tank.
So, if you are planning on doing mostly inshore fishing or cruising, I'd think you are fine with the OX66 engines. If you are looking at shooting out offshore on a regular basis and running 250 miles round trips, I would lean toward a newer more efficient engine. Just remember. Depending on how the engines were treated, it is possible that the older OX66s are in better condition than the 4 strokes.
When I upgraded to a four stroke from an OX66, my engine had 950 hours on it. The compression was still great and it ran great. However, I did like to go offshore on occation and I was looking for more range. The two stroke oil savings is negated by the 4 stroke oil changes. The noise was never a real issue but the 4 stroke is definitely quieter. And it is nice that I don't smoke up the marina after it has been sitting for a while. But the real reasons for the repower was the increased range and my peace of mind.
Decide on your needs, get the boats and engines checked and surveyed, and make an objective decision. Just my opinion.
Best of luck with your decision.
