I think Rick and Ron are making excellent points well worth heeding. If an engine manufacturer says fine, use the expensive waterless stuff, then fine, go ahead and use it. But assuming that because it has two properties--- no water and the ability to go to 375 degrees-- there are no other coolant properties that are important to your engine might be a mistake.
Also, I rather like the fact that if one of our engines starts to overheat it will quickly start blowing coolant and steam because we will smell it immediately at the helm directly above the engines (we never drive from the flying bridge and this is one reason why) and be able to do something about it before the engine destroys itself from overheating,which as Rick said will occur long, long before the engine gets to 375 degrees.
While our engines have overheat alarms I learned years ago that the primary purpose of an alarm is to tell you that the component it is guarding has just failed catastrophically.
So alarms are nice to have but I don't put my total faith in them.
As to the cost issue, the trend today seems to be to not replace coolant on a schedule--- every year or two years or whatever--- but to test it to see if it's properties are still intact. If they are, don't change it. The test is apparently a simple thing that takes just a few minutes. So where convention may have you changing coolant on a regular basis, it may be that you can actually go a long, long time with the coolant that's in the engine now.
So there is an element of "if it ain't broke don't fix it" here. I think Rick is correct in saying that the fancy expensive "high-tech" coolant won't make your engines run any better. And when you consider the potential downsides--- it might not even be right for your engine and it may reduce the chances of your catching an overheat in time to prevent engine damage--- it might be smarter to stick with what the engine manufacturer recommended to begin with.
If we were talking gas engines here it might not matter. If your experiment didn't work you can buy a new engine for cheap. But given the cost of repairing or replacing a marinized diesel I would be reluctant to experiment with it without the manufacturer's blessing.
PS-- When you say no water so no electroysis, are you talking about the heat exchanger? Because if you are, your coolant may not have water in it but I'm pretty sure the salt water the raw water system is pushing through it has water in it. In fact, that's the water that will facilitate electrolysis if there is a problem of that type on your boat.
