Thanks for the thoughts and idea. A number of used o/bs for sale are on
stands, off the boats they were on. So, and "in the water" trial isn't
feasible.

A number of dealers do have dynos, and will do a dyno run for you for some
setup fee.

I just thought maybe a dyno run under load, at full throttle, would be about
as good as I can do in assessing the o/b condition.

I've been told that the o/bs, in general, lose maybe 1-2% of their power per
year due to normal wear. If this is so, and is factored in, then the power
attained at full throttle, the duration of the test run, and the load
imposed are all good gauges of the overall condition.

Some sellers, of course, won't be bothered with letting me do a dyno run on
their o/b.