Modern marine engines have come a long way from the sputtering, oil-dripping beasts they used to be. Electrical systems with smart chargers, inverters and advanced sealed batteries are light years ahead of the leaky blocks of energy that used to start our engines and power our coffee makers.

Despite these improvements, items still wear, and parts break down. The challenge for the vigilant boater is to monitor the vessel’s systems in a measurable way so you know when something is wrong before it keeps you tied to the pier on a beautiful weekend morning or calling for a tow when you’re adrift.

Establishing a baseline

In order to know when something is not running right, you have to first know what “right” is. That means establishing a baseline against which you can compare ongoing performance. I’ve cut and applied a thin piece of blue electrical tape to my instruments at the position where the gauge needles should be at our normal cruise rpm. This lets me know at a glance whether everything is running “right.”

It’s easy to determine what “right” is when a boat is new, but it can also be determined for a boat you’ve owned awhile. It should be measured when the bottom and running gear are clean, the engine has fresh oil and coolant, and the heat exchangers are clean and free of restrictions or growth.

You’ll want to ascertain the engine data at your normal cruise speed, but it’s important to record data at other points, including wide open throttle. Record as much information as your instruments give you, beginning with speed at various rpm. Most factory instrumentation will also provide oil pressure, coolant temperature, battery voltage and rate of fuel burn. A diesel’s instrumentation will provide additional important data. Consult your engine manufacturer for the correct specs for your engine.

Next, build a spreadsheet listing engine data in four increments: idle, cruise, fast cruise and wide open throttle. Every couple of outings, run your boat at each of the rpm on your spreadsheet. Compare the values on your instruments against your previously recorded data. Variances could indicate something as simple as a fouled bottom or more serious issues, such as reduced coolant water flowing through the heat exchanger.

Adding instrumentation

Not all helms have the same complement of instruments, so make additions or modifications as needed to have all of the information you need. For example, we installed a pyrometer and added an exhaust temperature gauge to our helm. Exhaust temperature on a diesel is one of the most important items to monitor, second only to oil pressure. It can be a lone leading indicator of problems before they show up in any other way and, most important, before additional damage is done to the engine.

Taking its temperature

When people run a high temperature, we know they’re ill. Many of the components on your boat are the same. Knowing the normal operating temperature of items will help you monitor performance. Alternators, hydraulic systems, transmissions, battery chargers and pumps are just a few of the items whose temperatures can be monitored with an infrared temperature gun. These are inexpensive and readily available. I consider it so important to the operation of our boat that I keep a spare in the toolbox.

Engine room checks

Performing engine room checks while underway is about finding problems before they cause serious damage or leave you adrift. Regular checks have helped us spot a valve stuck in the open position on a hydraulic pump and a failed voltage regulator that was overcharging a battery — all discovered with the infrared temperature gun. I have a list of items to monitor in the engine room. I do the first check one hour after getting underway, then every few hours, depending on the duration of the trip.

Some engine rooms are easier to access while underway than others. If you don’t have a walk-in engine room, one of the advantages of the infrared temperature gun is that you should be able to read many important temperatures just from lifting a hatch. Always make sure you utilize safe engine room practices, such as wearing hearing protection and removing loose clothing when working around a running engine.

The lifeblood

Oil is your engine’s lifeblood, and having a “blood test” is critical to knowing the condition of your powerplant. Have your worn oil analyzed to establish the baseline. An inexpensive analysis at each oil change can reveal changes in the wearing of parts or internal components that are out of specification.

Stuff happens, but knowing how your boat is supposed to perform and regularly monitoring that performance will result in timely maintenance instead of costly and inconvenient emergency repairs.

This article originally appeared in the August 2015 issue.