"Jim Stewart" wrote in message
. ..
Does an engine past TBO make an aircraft
non-airworthy? I can't seem to find a
straight answer on the web.

TBO is a manufacturers recommendation, it has noting to do w ith
airworthiness. Some aircraft are not airworthy 100 hours after TBO, while
some run well past the number.

http://www.avweb.com/news/savvyaviator/187037-1.html
The Savvy Aviator #4: Debunking TBO

Engine TBO (time between overhauls) seems to be one of the most
misunderstood concepts in aviation maintenance. There are lots of
TBO-related old wives tales that are widely believed by owners and mechanic
alike, and they can cost owners a great deal of money. Mike Busch endeavors
to clear up these misconceptions, and explain what TBO really means.