Cooling

Direct Cooling

Direct cooling is done by using the fresh or salt water brought in by the seacock which is pumped up to the engine then pumped through and around the engine until it is discharged out the exhaust. This system will require a water or circulation pump and a water strainer, some engines have trouble with this system as most engines use radiator coolant in a closed loop system which means the cool water running through the heads can be to cold  for the engines running temperature.

Indirect Cooling

What is the purpose of a heat exchanger and how does it work?

The purpose of the heat exchanger is to keep the water cool and create a transfer of heat from one liquid to another through a solid surface. It uses hot engine coolant which is past closely to cool raw water in plates or through pipes. The heat is transferd from the cool water to the hot coolant and vice ceversa so that the engine coolant temperature drops and the cool waters temperature rises before it is discharged out the exhaust.

What is the core of the heat exchanger made of?

The heat exchanger core can be made from a number of metals but they are mostly made from alluminum, copper and stainless steel which is the least expensive compared to heat exchangers that use nickel, titanium cupronickel.

What is the purpose of a thermostate?

The purpose of the thermostat in engines is to stop the coolant flowing through the cylinder block and engine untill the engine has reached its operating temperature . The thermostat is mounted on the side of the engine block which is normally at the top of the radiator hose inlet and as the temperature rises to its set temperature the thermostat opens up which allows the coolant to flow throughout the system untill it drops below the temperature then the thermostat will close again. 

Radiator Pressure cap?

The radiator pressure cap is mounted on the top of the radiator where the radiator is filled, the pressure cap opens up a specified pressure where it lets the pressure out and directs the fluid out into the overflow bottle or on to the ground. For different vehicles the caps will have different pressure ratings if you have a faulty pressure cap it could cause overheating and engine damage from getting to hot. It uses a spring which opens up when the cooling system has reached a certain temperature and pressure to lower the boiling point.

Why and what is the purpose of a core plug

The reason why we have core plugs on engines is for manufacturing purposes when the block is being cast and it is put in to remove all the sand and debri from the block once it has been cast. They are small plug holes in the side of the engine block and are also there for cold climates where the coolant freezes and expands which will pop out a core plug instead of cracking the cylinder block.

How does the centrifugal circulating water pump work?

Centrifugal pumps have a housing with rotor type impellor's which spin on a shaft and makes the water passing it speed up and increase the flow of water which will be pumped through the system until it comes back to the pump. This pump converts the mechanical energy from the moving impellor to increase the overall pressure of the coolant.

Why is it important to lubicate the impellor when fitting from new?

When fitting a new impellor you must lubricate the housing and impellor with marine grease of some kind of lubricant or it will run dry and can cause more wear and stiffen operation.

When fitting a impellor what should you check before refitting the housing and why?

When fitting a impellor you must check that the impellor fits without play and the that the housing and gasket go in place evenly.

What is the purpose of a oil cooler and how does it work?

The oil cooler is put in place to remove the hot oil from the engine and run it through  the oil cooler which has fins that cools the oil down then it is replaced back into the engine this helps to keep the engine cool and to raise the boiling temperture of the oil.


What is the process of a intercooler/aftercooler how does it work?
The intercooler is put in place to cool the air and increase the density of the air flowing through it as it is forced through the fins of the intercooler as air is passing around it which cools the air  and makes it more dense .

Why do we have Inhibitors & antifreeze?

Antifreeze is used to lower the freezing point of the coolant so the engine doesnt freeze up and crack the block and it can raise the boiling point of the coolant . And it helps to stop corrosion and flaking in the system. Different climates and engines will use different grades of antifreeze

How do you test Antifreeze?

By buying a antifreeze tester and waiting at least 15minutes till your engine has cooled down enough to work with. Then with your antifreeze tester you suck up the coolant in your radiator which will make certain floats inside the tester rise then depending on how many balls rise inside the tester will tell you what percentage of the coolant is antifreeze. Different climates and engines will require different percentages.

What is cavitation corrosion?

Cavitation corrosion is caused by a liquid fluid running past metal or rubber components and create cracks and splits on the surface of the material it is said to be caused by an implosion of gas bubbles onto a metal surface.

What is galvanic corrosion?

Galvanic corrosion is caused by two electrical components that are touching to corrode into eachother it is a electro-chemical reaction.

Stray corrosion?

This is called stray curent corrosion as it is created from the battery and alternator charging system not having a good enough ground and the voltage tracks through the radiator and system causing a electrolytic corrosion.

Stress corrosion?

Stress corrosion is also known as SCC (stress cracking corrosion) which affects most of the metals by cracking under high pressures, temperatures and exposures which cause the metal to crack. Some SCC look bright and shiny but when you look close there are microscopic cracks which go undected.



Crevice corrosion?

Crevice corrosion is caused by small gaps and crevices where water or fluid collect and cant run off which causes corrosion to start and build up between the two surfaces.

What is Electrolysis?

Electrolysis is a corrosion which affects electrical components which decomposes the metal and corrodes connected components

Why and what is bonding in the marine industry?



Bonding is when you connect all the components that are metal to a common earth strap for corrosion devices and will remove the stray current from electrical components and so there is a secure earth for all components.

What are sacrifical anode made off?

Anodes are made from zinc and are mounted in the stern drive or outboard on metal components which it draws the salt and helps protect the boat from corrosion.