Will it Safe Boot if you hold the Shift key...?
see > Mac OS X: Gray screen appears during startup
Can you startup from your Recovery Partition if you hold the Command R keys..?
see > OS X: About OS X Recovery
If you startup into the Startup Manager by holding the Option key, can you see and select either your Macintosh HD or the Recovery Partition...?
see > Startup Manager: How to select a startup volume