[Lemonshark]

I recently installed a 3 bladed Indigo prop on my 1977 Catalina 27.I doubt if this is related to the problem. I ran the motor full throttle for a half hour or so and noticed the temperature gauge reaching 200. I shut the motor off and sailed back home, but could not start the engine when I got there--it turned over fine but did not even try to fire. A friend and I put new plugs and points in (the points appeared fried) and it starts, but runs only at higher rpm's. When I try to idle down, it quits. We tried adjusting the timing and adjusting the idle screw on the carb, but no luck. The engine used to start without using the choke after it had run for a while but now it needs to be choked every time to start it.
My first question is how to get the engine to idle, and my second question is did the overheating have anything to do with the engine not starting, and I guess my third question is what would cause the overheating. I have water coming out the exhaust and just last year flushed the system (raw water) with muriatic acid.