Hello...<br />I have a 1983 470/alpha that overheats.<br />Not new?<br />I have a new 4" heat exchanger,new stern pump, new exhaust elbow, and have determined that the engine water pump pumps. <br />The critter seems to overheat under the following conditions:<br />Under full or near full throttle (4000 rpm), after an extended period (about 30 minutes at full). This occurs with or without the thermostat in place.<br />Two things that I see happening are: the overflow tank fills with coolant when run after the system has been "topped off", and then some bleeds into the bilge. Not all of the coolant is sucked back into the system after cool down.....there is a vacuum in the system, and about a pint of coolant may be added. I believe that overheat occurs quicker when the system is not topped cold, that that pint makes a big difference.<br />Is it possible that the overflow is too small? Would I be better running a hose from the expansion tank on the motor to the overflow container? <br /><br />I have retraded the timing as well, although that seemed to make no difference.<br /><br />Thanks for the thoughts!<br />Peabody
