When doing a search on Google just 10 days ago – my site was on page 4 in results using a simple keywors "skiffs" (I build boats)
Now I am on page 7-8… I cannot figure out how in the world this happened.. I made a few MINOR changes but nothing I can really trace back….
There are a million reasons why your site could have dropped in the SE. It could be anything from someone hacking your site and secretly putting a lot of hidden outbound links on it to Google changing their algorithm causing your site to drop. I would recommend posting on an SEO forum to see if they can help you with an analysis. They may also know about recent algo changes.