"I have a 1996 135 Mariner V6
"I have a 1996 135 Mariner V6 outboard and it overheats only when engine is working hard, ie, trying to get up on plane. Temp OK up to 2000 rpm, overheats between 2000-3500 rpm, then temp comes back to normal when above 3500 rpm. I have replaced both thermostats...