One of my Centova Cast's MySQL DB is at 140MEG, I think it caused it to crash I ran the repair MYSQL command and it's fine now but it will most likely happen again

Any1 know of a way I can trim the logs?

A 140MB database is not in itself a problem at all... it's common to have databases that are gigabytes in size.  (Obviously you wouldn't have a DB that large with Centova Cast, but MySQL is capable of handling databases of that size).

If you want to trim your event log though you can do so via the MySQL console, just run:

DELETE FROM eventlog WHERE DATE_ADD(eventdate,INTERVAL 7 DAY)<NOW();

That'll delete everything older than 7 days.  I should add a feature to do that automatically from the user interface.