The "cooler" supplied by ZF is a simple heat sink. After my 2nd failure I changed to a bigger gear
. Read the ratings very carefully and check your shaft alignment.
I was getting 230 F+ readings on the zf10. After repowering I chose a PRM Rated at twice the continuous HP and cannot get it to heat above 130 F.
ZF bought Hurth and both thought you were just going to the bouy's to race