Basically I am working on a sharepoint site, but the company I am working for have not given me central admin access. We have created a custom search and need to filter some list searches by columns. Is there any way to do this without adding a managed property?
No. In Search the only thing you can search on is free text and managed properties and the only thing you can retrieve is managed properties.
And then again, it depends. If you're only searching for data inside a single site collection then you may be able to use SharePoint 2010 Site Search, which behaves like search, but really transforms the query into CAML and does a query instead of a real search, but that doesn't support real free text search.