Yanmar Marine Diesel

Learn to understand your marine diesel engine cooling system is a necessary element of basic marine diesel engine maintenance.

On the raw water cooling

A flexible impeller pump provides an effective solution to the water most of the first pumping needs. The main advantage of flexible impeller pumps is that they are self-priming, which means that when the turbine blades are depressed and rebound, they create their own vacuum drawing fluid into the pump. A dry pump can lift water up to three meters. Thus a flexible impeller pump used for cooling the engine did not need to be manually started or located below the waterline. An additional feature of a flexible impeller pump is that it can pass solids without large enough to obstruct or damage the pump. This reduces the need for filtering incoming liquids.

For general applications or fresh water, a standard long-lasting neoprene rubber wheel is used.

A general feature of all flexible impeller pumps is that they can not be allowed to run dry for more than 30 seconds. Both the wheel and the joints need water for lubrication and will soon disappear if the dry run. The pieces are starting to show wear are easily replaceable and maintenance kits are available for most models.

Freshwater cooling

For the circulation of the interior, closed circuit fresh water cooling system, it is common to use a soft rubber pump if it is located on the cold side of the system (max. 55 ° C). Other types of belt centrifugal pumps are also used. The closed circuit normally transfers heat from the engine heat exchanger. The liquid used is water and antifreeze.

Cooling Capacity

The production of the required cooling pump is related to the size and type of engine, not the size of the heat exchanger and exhaust system. This is true both for the raw water, as well as fresh water handling systems.

Temperature controllers (thermostats)

Thermostats are usually placed in the receptacle on top of the head to prevent the coolant to move to the header tank until the marine engine has almost reached its operating temperature.

There are different types of thermostats, the most common being the type of wax pellets. The capsule on the bottom of the thermostat is a mixture of wax and copper (to increase the thermal conductivity) sealed it. When the temperature increases coolant, the wax expands and forces a rod to open the valve at the top of the thermostat, allowing the coolant to circulate.

The cooling system controls

• To test your thermostat, boil a pot of water and lower the thermostat. (The water should be 100 degrees Celsius - the temperature usually opens at 85 degrees Celsius.) If the thermostat opens, it is good. If it does not open, replace or clean it carefully as they can become sticky with deposits. Yanmar thermostats can and must be regularly maintained. Some thermostats can not be repaired.
• If the thermostat does not work, do not remove it and run the engine without it, the engine is running cold and tight. You can drill a series of quarter inch? holes for the flow equivalent to a thermostat open. That you go home, but you need to replace it. Be careful not to mount the thermostat in reverse.
• Thermostat housings often corrosion and must be replaced. Some can be manufactured.
• The cooling system should be checked after 100 hours of operation, or at least once each season for leaks, deposits, etc.
• The thermostat can be removed from the box on t.