It would be a good idea to check the compression, do a leak down test if possible, and check the engine for any trouble codes. The other key things to ask or check would be, when the internal anodes were changed, if timing belt was done, when plugs were last changed, has vst been cleaned, when were the high and low pressure fuel filters done last, when was the impeller and gear oil changed, when were the valves adjusted, and when the engine oil was changed last. Any records would be helpful. It is also a good idea to find out if the updates were done. If the owner does not know, then you can call a Honda dealer with the serial # and they should be able to tell you what has been done. Another key thing to check for would be any corrosion around the thermostat covers or around any part of the powerhead, and if the midsection has corroded through where the driveshaft bushing is located. There is a small cover on the front of the lower part of the midsection, above the lower unit, that can be easily removed to show the area where the bushing is. I was not aware of this when I bought my pair of 03's and ended up buying midsections for each engine. I was fortunate I could find them for about $600/ea and do the swap myself. If you are not mechanically inclined, then I would spend some time looking it over or even paying someone to do it for you.
Don't let these things scare you off. All engines have some issues. The Honda's are good engines and can run for a very long time if taken care of. You just want to make sure you are getting one that was cared for, or at least getting a price that will allow you to factor in what may need to be done to it. A sea trial should also give you a good idea of how it is running. if you can take it to a local dealer, they can read the ecm and tell you about any codes, how long the engine was run in what rpm range, etc.
