I need to sort out some problems on my 78 Evinrude 85hp. I have been told to check the spark by removing the spark plug boot and inserting a screwdriver into the boot. Then hold the shaft of the screwdriver 1/2 inch from the block and see if the spark jumps the 1/2 inch gap. Is this the best way to test spark? Also are Craftsman screwdrivers "insulated"? If not what is an insulated screwdriver? Thanks in advance.