Removing heat from marine components using sea water presents some complicated
problems. Sea water is not just a solution of salt and water. It can and does
include many other minerals, bio organisms, chemicals in and out of solution,
gases, and etc. The actual composition varies with locality, temperature, and
depth from the surface. The free oxygen in the water combines with the salts and
produces corrosive chemicals that attack all known metals, some worse than others.
The degree of corrosivity varies with composition of the sea water, temperature,
and the amount of free oxygen in the water. Most marine diesel engines operate at
cooling water temperatures in the area of 180 to 210 degrees F. to improve the
With this in mind, we would like to direct your attention to three significant
areas of concern when using sea water as a cooling medium in marine engines.
- The corrosivity of sea water increases with temperature.
- Salt begins to precipitate from solution at approximately 135 degrees F. and
plugs the cooling passages
- Contaminates in the sea water, including pollution, fine sand, calcium
carbonates, etc. collect in the small crevices of the cooling passages,
And we haven't even discussed crevice cracking, impact pitting, galvanic action,
and a host of other potential problems.
In our opinion, there is only one solution for a water cooled engine. Use fresh
water, and transfer the heat to sea water thru the use of a heat exchanger. Of
course, the heat exchanger will be subject to all of the above potential problems,
but it is a lot cheaper to replace than an engine. Ask the question: How many
U.S. made diesel engines are sea water cooled?