[roywmoss]

My 5411 operating temperature seems very much a function of the seawater temperature. In warm water it seemed to run about 200 degrees or more (run at max rpm for hours on end) and it was exhausting the paltry amount described in one of previous posts. I was unaware there was a thermostat and I installed a manual ball valve in the recirculation hose to adjust/stop recirc. in warm weather. By eliminating the recirc., it exhausts twice the water, which I find reassuring. It may operate below optimum temperature (a supposed diesel no-no), especially in cold seawater, but perhaps this will reduce buildup in the cooling channels and explains its (27 years) longevity?