Originally Posted by
swimjig180
2010 Mercury 250 pro xs. Serial # 1B751217<br>
I was attempting to change my spark plugs today when I found a couple spark plug holes to be cross threaded. I got the old plugs out but cannot get new ones in. I feel comfortable chasing the threads with a back tap or regular spark plug tap. My question is how involved is removing the heads to ensure no metal shavings get in the cylinders? Or is this necessary at all? It looks pretty straight forward to me but I’m sure I’m missing something. Do you have to replace gaskets, o rings, & bolts when you re-install it? Thanks in advance.