[spareparts]

a raw water pump is probably what is wrong, they are notorious for going out. a simple compresion check will tell you if the head gaskets are shot( it may not indicate if they are cracked however). An easy way to check the water pump is to pull the hose off the thermostat housing that comes from the power steering cooler, look in there to see if you see any pieces of impeller, hook a flusher up and crank the engine up with the hose off, you should get a nice steady stream of water, about what you would get if you cut the end off a garden hose and turned the spigot on. Another thing to check is the exhaust risers and manifolds, not a real good way to check them other than looking at the condition, and questioning the age, if the boat is in salt and the engine has been flushed regularly, expect 5 to 7 seasons if you're lucky, if the engine hasn't been flushed regularly, figure 3 to 4 seasons at best. The manifolds will stop up, not allowing the hot water to exit the engine, you may notice a burnt rubber smell associated with either of these problems, its the exhaust hose burning up due to lask of water mixing with it. A bad circulation pump can cause the engine to heat but usually the bearing will go out, allowing the main pulley to wobble noticably( i have seen the circulation pump impeller rust off inside the block,its rare but can happen). *Stuck thermostats can cause overheating as well. If the alarm went off, they are usually set at 215( what good is an alarm that tells you its too hot too late?), most new cars run that temp everyday, so you may be ok on the engine

Check the water pump first, then inquire to the age of the manifolds( they can be expensive)