best temperature at which to run raw water cooled engine

[Amphibiographer]

Greetings forum friends.
Can someone tell me at what temperature the salt begins to precipitate out of raw water? Is it better to run the Atomic 4 cooler so this doesn't happen? What temperature is best for running an Atomic 4 on raw water cooling?

A friend runs his raw-water cooled Atomic 4 without a thermostat. He's a real sailor and doesn't motor unless absolutely necessary. I have to run my RWC Atomic 4 most of the time I'm using the sailboat because I am doing a lot of video of whales and sails get in the way. Could I get away with not having a thermostat? Without one my engine runs about 130degrees when water temperature is about 58 degrees.

Thanks for advice.

[roadnsky]

This is from Don's FAQ's....

"Like all internal combustion engines, the Atomic 4 would like to run around 180 degrees. However, the designers were concerned about salt precipitating out of sea water at temperatures much above 150 degrees, so they installed a thermostat rated at 140 degrees, which in most areas will maintain an operating temperature between 150 and 160 degrees (depending on outside water temperature).

Several years ago, Westerbeke came out with a 180 degree thermostat for people operating in fresh water areas or for engines with fresh water cooling systems installed, particularly in cooler climates (like the Great Lakes, Lake Champlain, etc.). In our experience, the 180 degree thermostats create a few problems in warmer waters where just a small amount of fluctuation in operating conditions can cause temperatures to overshoot into the 200 degree range. Effects of running in the cool range (95 to 100 degrees) include increased carbon buildup on valves and rings. Eventually, both the valves and rings can stick, and compression will suffer. Of the two effects of running too cool, sticky rings are the more difficult to cure."

[Al Schober]

I ran my A4 without a thermostat for years without a thermostat. I eventually changed to glycol/heat exchanger and continued without t'stat. Just one owners experience of 30+ years.
The temp gauge is a funny thing. Just for fun, I recommend you buy/borrow an infrared thermometer and poke it around your engine. I did so and concluded that the sensor at the flywheel end of the head was lying to me. I moved the sensor to a tee at the outlet from the manifold and felt that it gave me a better handle on water temp. The stock location gets poor water circulation and seems to me to read head temperature rather than water temperature.
The folks that really watch head temperatures are the ultra-light aircraft folk. They put their red line at about 400-450 F or so, depending on the engine.
But you'll always be subject to those days when you head out without opening the intake valve!

[Amphibiographer]

Thanks so much for this info. I searched the internet for over an hour asking "at what temperature does sodium chloride precipitate out of sea water" and couldn't find the answer.

Since the Atomic 4 is running 120 - 150F I'll continue with raw water cooling and get a 140F thermostat if I can find one.

[roadnsky]

Please note that many on this site are true believers that converting to a FRESH water system is one of the very best things you can do for your engine.
(I am one of them)

Of course, it is your vessel and your "Boat Bucks" !