How to increase the MAX hop count

[net admin]

Hi Folks;
I am seeing a bunch of message delivery failed bounces that says:
Too many hops 27 (MAX 25) ...
since almost all the bounces were just a couple of hops more than the max I would like 
to increase my max hop count to, say .. 30, how do I do this and what are the gotchas 
if any?

Dan   Thanks