This article is very informative. I did a lot of research and talked to a couple well respected accredited surveyors that confirmed what this guy says. I didn’t buy a meter. Go with what Phil T said.
http://www.pcmarinesurveys.com/Moisture%20meter%20mythology.htmA few adds:
Ask the seller for maintenance records. That will tell you a lot.
So will whether the vessel meets all CG standards. Lights in order? Pfd’s in good shape? Fire extinguisher? Signal device? Horn works? If kill switch installed, does the owner put it on his person or ignore it? If there’s a lot of deficiencies, you gotta ask “if this person doesn’t care about their and their crew’s personal safety and the safety of other boaters, why would you think they take care of their boat any better.
For the love of all things holy, is the trailer safe with working lights, good tires, bearings, safety chains? Same concern if it’s not. Folks who drive unsafe trailers should be ticketed like drunk drivers. The consequences when things go wrong are usually very serious, often involve other people, and are permanent.
Spark plugs. But if they’ve just been replaced, not helpful.
Water emulsion in lower unit oil.
If 2 stroke, crankcase leak down test.
Sea trial will tell the most. Per the comment about water line, see where it sets at rest. If she sits low, that’s a problem.
Sea trial, rpms at WOT to see if propped relatively good (should be within engine spec for range of rpms at WOT - neither lower nor higher). Also Check mph at WOT.
Steering is critical. Test it thoroughly. Same as the trailer if it’s not ship shape.
Good luck.
ETA: for my next boat if I’m so lucky (bought four, three used one new, and built one) I will shorten the process. Walk around for general condition / records / lights and equipment in serviceable condition, wiggle transom, check for soft deck. Done. Sea trial - if it starts easily over and over, tell tail and temp gauge okay, accelerates and runs well, mph and rpm in spec, and steering and handles good on the water, including sitting where it should in the water. Check. Trailer set up properly for the boat and in good condition. Cool. Study the seller and how many prior owners have there been. Cool. Price right and I can afford the inevitable costs. Done. No compression check, leak down, tapping hull. I’d look at that only if something was not feeling right.
