My C152 has about 7500 TT logged but the hobbs shows about 3900. Does
this make any sense? Perhaps the hourmeter was replaced?


Most likely. As an A&P I look only at the recording tach reading rather than
hobbs. Some hobbs have been wired to run when the master switch is on while
the tach only runs when the engine is running.

When looking over logbooks one thing I always highlight is any tach
replacement. I have found aircraft with four tach replacements with no one
really following through on total time when removed. Took hours to extrapolate
an approximate total time.