Room Temperature (Cooling)
One of the biggest culprits in engine problems isn’t, technically, a part of the engine. At least not one covered by warranty. Berlin says this: “Clogged sea strainers are the number one cause of failed engines.” Fouled strainers prevent raw water from cooling the fresh water, which throws off the whole system.
A marine engine’s cooling system consists of two basic components. The raw-water system draws in seawater through an open seacock via an in-line pump. The seawater goes through a lube oil cooler and then to a heat exchanger, where it cools the engine’s fresh water. It then runs through the mixing elbow, where it cools the 1,300-degree F exhaust gas before exiting via the exhaust system.
The freshwater system is a closed loop that pumps water from the reserve tank to the cylinder jacket, turbocharger and cycle head. After start-up, a thermostat in the system regulates a valve that cycles the heated water through a heat exchanger, where it is cooled by the seawater.
Discussing this in the classroom, Berlin holds up a circular piece of rubber that looks like it’s been assaulted by a weed whacker. It’s a raw-water pump impeller gone bad. Impeller failure is another problem that gets him into the field on an hourly rate.
A healthy pump impeller looks like a gear, with rubbery veins that spin and flex as the pump does its work. Impellers absorb seawater over time and harden, causing the veins to warp, bend or break off. Once its veins bend or harden, it will never pump the full amount of water your engine needs.
Berlin suggests it’s best to remove the impeller in the fall and put in a new one every spring, but at the very least take it out. Removing the raw-water pump requires a socket wrench to take the pump off the block and an impeller removal tool, which is kind of like a wine rabbit, to pull it from the housing. (You can buy an impeller remover for $100 to $150 from your marine supply store.) Before you put the new one in, coat the inside of the pump with the provided glycerin or extra virgin olive oil.
Putting the pump back in place requires more thought than removing it. Every bolt on the engine — indeed, every hose clamp — has a specific torque spec and tightening sequence. Look through your engine’s service manual to follow the specified tightening pattern, and use a torque wrench to tighten it to those specs.
On the freshwater system, the easiest thing to maintain is the pressure cap. It needs to be properly sealed so that it increases the pressure enough to raise the boiling point of water from 212 degrees F to 250. Otherwise the water in your engine will boil and your system will overheat. Look for a bent cap — they often get stepped on in the engine room — or a faulty seal.
Also, change the antifreeze every two years, using only an extended-life brand (think pink not green), and mix it only with distilled water.
Berlin shows us other, more complicated maintenance projects, such as removing the heat exchanger to send it out for cleaning. It needs to be done every three years. On most engines, the removal is a three-hour job involving disassembly of other parts and fittings. On common-rail and electronically controlled engines, it’s not to be touched by us at all.
Moving on to something more our speed, Berlin holds up an old mixing elbow, the macaroni-shaped part that funnels exhaust and seawater from the engine. He instructs us to look inside — it is nearly completely blocked with scaling and corrosion. “These need to be changed every three years,” he says, “but nobody ever does it. Then they call us.”
On the freshwater side, a part to keep an eye on is the thermostat. It opens and closes anywhere from 100 to 1,000 times a minute to regulate coolant flow. Though incredibly reliable, these do eventually break down. Berlin shows us how to do a field test. Remove it from the engine and run a thread through the release valve. Hold the top of the thread and drop it in water and boil it until it falls off the string. Then measure the water temperature that opened the valve and the length of the opening hole. If not up to spec, replace it.