FWIW:

It is interesting that I had a TSIO 550 stored for about 7 years and the
alternator coupling was bad, also.

Other than that, the engine (TT) has been fine.

Michael D Smith



and our only significant engine problem so far,
was with the coupler on the alternator.  It was defective and I am not sure
if it deterioriated while in the "pickled state" but we ended up getting a
new one from Continental (at first they refused, and told us we had not
warranty) after our engine shop go on the phone and helped out.