How to limit phpbb's search function

I have a large phpbb forum that was recently dumped into my lap开发者_如何学Python and the search function is really eating up my server resources.

I am looking for a way to stop the query after say 500 results. It is my understanding that the sql_query_limit function could take care of this issue but phpbb's search functions are above my knowledge level.

Any help being pointed in the correct direction is greatly appreciated.

phpbb won't allow to search more than 50 results by default