I have a 1991 BlueWater with a 4.3 L mercruiser motor in it. Recently I have noticed the smell of antifreeze when I turn over the motor. It also has been missing once in a while when I am over 3000rpm. No leaks in the hoses but am wondering if this is a sign of leaking head gaskets. The temp gauge has also be jumping all over the place. Any suuggestions?