Alright 1976 OMC 165 overheating at odd intervals with other strange symptoms. Temp will get stable at 160 ish and then slowley start to rise and inlet hose felt hot so i thought i was sucking up exhaust in the swivel housing. I replaced the thermostat and checked the seals and repacked the swivel housing and it was fine. But i put on a clear hose on the inlet line from the outdrive to motor. This time no air bubbles coming thru but after 10 minutes it seems to build up back pressure and stop the water flow. I shut it off and alot of air, steam,and bubbles blow backwards thru the inlet line. Once stable i start it again and water flushes thru cools it to 160ish and slowly builds pressure again and stopping flow. No idea where to start with this one. Thanks ahead of time.