There are a couple of reasons for setting a limit on search hits on a message board. One is that few people will read more than a few of those messages, so you try to pick a number that is a reasonably high enough count to cover most bases. A second reason is that searches are very intensive on server resources. So considering point 1 above, if it is unlikely that anyone is going to view the results of the search beyond a certain number of hits, then why bother making the server deliver those hits for a user and waste the resources? Lastly, malicious people can cause some severe throughput problems on a message board server by sequentially triggering searches on keywords that would produce a large number of hits. This drags down the server processor considerably, which will cause all users to get frustrated at the system slowness that results.
This software has options to limit such activity, but in all cases it is a case of trying to figure out what is the best tradeoff between user usefullness and keeping the cretins from wreaking havoc with the system.
I have upped the hit count to 200. See if that is more accomodating to your needs.