I consider myself a pretty good driveway mechanic and have quite a bit of experience with automobiles, some aviation, small engines, etc. I am also a retired engineer. I am new to marine powerplants. I am working on an overheating problem on a Merc 5.7 (see separate posting), and need some help understanding all that strange stuff bolted to the engine.<br /><br />1. Why 130 deg.? A few years ago cars ran at 160 or 180, but modern cars run at 195 or higher. My understanding is that the trend to higher temperature was driven by emissions and economy. So why does the same Chevy engine run at 195 in a Chevy and 130 in a Cobalt? I say "same" meaning the basic engine. I know the cam is different, but pistons, crank, bearings, compression ratio, fuel, etc are just like a car.<br /><br />Is it safe to run the engine at, say 160 or 180, not all the time, but say for an hour or two.<br /><br />2. Can someone direct me to a good explanation of the why's and how's of the exhaust system (manifold, risers, elbows...)? <br /><br />3. Why are there two separate water lines going to each manifold. <br /><br />4. What is the purpose of the ball check valves near the thermostat? I'm guessing that there is a venturi in the manifold that sucks water out of the block?? <br /><br />5. Thus, it would seem that the cooling system is not pressurized much, if at all. How about the fresh water inlet to the block. Should there be a measurable pressure here?<br /><br />I realize that this is too much to cover in a simple message, but is there a book or something that explains the theory of all this.<br /><br />Thanks!
