Marine Engine Heat Exchanger, Intercooler and Cooling System Service

The most common causes of overheating are scale and marine growth in the heat exchanger tubes, a worn impeller or one with missing vanes, a blocked seacock or sea water strainer, pieces of eroded zinc anodes blocking the passages, a faulty thermostat and a loose belt. If your engine overheats, reduce RPM until the temperature gauge returns to normal and let the engine cool at idle; check the raw water discharge and do not run at high RPM until the cause has been found.

The heat exchanger is removed from the engine, the end caps are opened and the tube bundle is first rodded out tube by tube. It is then chemically cleaned with a marine descaling solution suited to the tube material and neutralised with plenty of fresh water. Gaskets and O-rings are renewed, the unit is pressure tested for leaks and refitted to the engine.

As a general rule, every 2–3 years or at the interval recommended by the engine manufacturer. The interval is shorter for boats used frequently in warm, hard water. A gradual rise in operating temperature is a sign that cleaning is due.

Tube expanding (rolling) means expanding the tube ends where they sit in the tube plate with a special tool to make them watertight again. It is applied when the pressure test shows leaks at the tube ends. If the tube itself is holed or thinned, that tube is plugged or the tube bundle is renewed.

The intercooler cools the hot intake air coming from the turbo, so the engine runs more efficiently and at lower temperatures. Oil and soot build-up on the air side reduces performance. On a seawater-cooled intercooler, a holed tube lets seawater into the intake air and the cylinders, which can cause severe engine damage. That is why the intercooler should be cleaned and pressure tested regularly.

Zinc anodes protect the engine block and heat exchanger by attracting galvanic corrosion to themselves, so wearing away is normal. Stray current in the marina, a bonding problem on the boat or low-quality anodes accelerate the wear. Anodes that wear much faster than expected indicate that the boat’s electrical system should also be checked.

Engine and heat exchanger zinc anodes should be checked every season and replaced when about half worn. Pieces of fully eroded anodes can break off and block the heat exchanger tubes, causing overheating. When replacing an anode, the residue in the anode seat should also be cleaned out.

The seacock is the through-hull inlet and valve through which seawater enters the boat. If it becomes blocked by mussels, marine growth, plastic bags or weed, the engine’s cooling water supply is cut off. Regularly operating the valve and checking it for leaks is also important; a seized valve cannot be closed in an emergency.

The sea water strainer should be checked visually before every trip and cleaned whenever it is dirty. This is even more important for boats used in weedy or dirty water. The strainer lid gasket must be in good condition; otherwise the pump draws air and cooling efficiency drops.

For seacock lines where standard strainers do not fit or special dimensions are required, we manufacture stainless steel and special-alloy sea water strainers in our own workshop. The strainer is designed to suit your boat’s line diameter, flow rate and installation space.

The antifreeze coolant in the closed cooling circuit should generally be renewed every 2 years or at the interval recommended by the manufacturer. Over time the protective additives are depleted and the risk of internal corrosion increases. When the coolant is renewed, the system must always be bled of air.

Yes. We carry out heat exchanger removal and refitting and cooling system maintenance on site in marinas, boatyards and winter storage yards across Turkey. Chemical cleaning, pressure testing and tube expanding are completed in the workshop when required.