Search engine

I need a good site search service or offering to run on a few of my sites. I currently use Dansie Search Engine (running on my own server) for a retail site with about 750 pages, but it is incredibly slow (30 to 45 seconds to complete a search).
I have looked at the Yahoo and Google site searches that you can put on your site, but the results show PPC advertising from competitive products/offerings.

Are there any good site searches that do not show ads? I do not mind branding or showing credit for the engine providing it, but I will not use a service that might provide doorways to customers to leave through.

If not, do you have any recommendations for search scripts to purchase and run myself?
Both of those two still either include advertisements or do not grant commercial usage.