my 68 650 merc doesnt have a overheat alarm i got it hot last year and real hot it cracked the water jacket at the spark plug just a seep but it seems to run fine after i found broken wire from switch box and rebuilt carbs can a over heat alarm be added to this engine and how i sure hope i didnt burn up any pistons with overheat after reading all the info from you guys on here its serial numb 25352154