Engine Room Inspection: Part 1 - Set a Routine

When two clients ask me, in the same week, if I’ve written an article on a particular subject, I pay attention. In both cases I’d recently completed reviews of their vessels, one in-person, for a 17-year owner, and the other remotely, for a foreign buyer. During the ensuing discussions a range of subjects were covered, from correcting defects to improving the safety, reliability or operation of specific systems or components, which eventually led to, “What do I look for when checking the engine room while underway?” question.

Engine Room Round Robin

There are two kinds of engine room inspections, one is static, and performed while dockside with the engines and genset stopped. The other is done underway, with engines and other gear running.  In this article I’ll cover the underway inspection.

Before venturing into the engine room, make certain you are properly prepared. This includes eye (I wear reader safety glasses whenever I work, and especially around moving machinery, hot coolant, oil and hydraulic fluid etc.) and ear protection, while ensuring you are wearing no jewelry that can catch on machinery or conduct electricity, which includes metallic rings and watch bands, and you have no loose clothes, drawstrings or exposed ponytails. I make it a point to wear shoes in machinery spaces, even if the boat is shoeless, as they offer better footing, while protecting my feet and especially toes.

A few years ago, while performing an underway inspection in stocking feet, I slipped on a slick gelcoated deck, and my foot made contact with the rotating shaft coupling, which was equipped with a safety wire-secured set screw. The sharp edge of the wire caught my sock, yanking it cleanly off my foot. I was unharmed but it left me startled, with a lesson learned about being barefoot in the engine room. On one occasion, while conducting an engine-room inspection, just as I was about to close the door behind me, a coolant hose separated from a pipe adapter (it was in fact a threaded pipe nipple, which is inappropriate for terminating hose), which immediately released the contents of the engine’s cooling system and keel cooler, gallons of 195°F (90°C) coolant and vapor. After that sobering episode, I vowed to always wear safety glasses in engine rooms.

Safety First

If that lesson isn’t clear enough, I’ll reiterate; you must remain alert while performing these underway inspections, especially while you are near moving machinery such as belts, pulleys and propeller shafts, and hot parts, including the dry exhaust, turbochargers and turbocharger charge air plumbing. A misplaced finger, hand or forearm could end in a nasty burn or an amputation. I’ve experienced the former first-hand, and witnessed the latter, when momentarily blinded mechanic (he had just come from bright sunlight) lost his thumb after inadvertently placing it between a turning belt and pulley.

The tools that are needed for an underway engine-room inspection are simple and inexpensive, an infrared (IR) pyrometer and a small flashlight.  While the order of the items you inspect isn’t especially important, it makes sense to do so in a geographically logical manner, i.e., if you make a circuit around the engine room, inspect each item as you come to it, avoiding backtracking. Then make that your route every time thereafter. Once that route is established, prepare a checklist that you can follow, at least initially, as a prompt, to prevent you from missing anything.  

What to Check

Coolant: I’m a big fan of coolant recovery bottles because they serve as excellent visual status indicators for an engine’s cooling system. If an engine doesn’t have one, in most cases it can be added.  Using tape, mark the level in yours when cold, then again after the engine has reached its full operating temperature and has been running for at least an hour.  These two indicators will provide a quick visual reference, the coolant should return to these two marks when cold and hot, if it doesn’t, you’ll know right away something is wrong.

If you know where your engine’s coolant temperature sender is, using your IR gun check that, as this will confirm your gauge reading is accurate. It should be within about 5°F (3°C) of the gauge on the instrument panel.

Alternator(s) 

If your vessel has the ability to monitor alternator output specifically, using an ammeter for instance, you should make that part of every engine room check, even if the gauge is somewhere other than the engine room. It’s important to note, if you are underway, with a genset running, which in turn is powering a battery charger, it’s possible that alternator output will drop, potentially to zero. This is entirely normal, as the alternator’s regulator “sees” the higher voltage supplied by the battery charger, which signals it to reduce or eliminate its own output. Beware, however, this scenario can mask a non-functioning alternator, and as such it’s important to periodically confirm alternator output with no other charge sources present.

If your vessel is not equipped with an alternator ammeter, then you should consider confirming alternator output using a digital multimeter that is equipped with an amp-clamp. While many engine instrument panels will measure voltage, or net amperage, it is not a completely reliable means of confirming proper alternator function, as that volt meter will register voltage and current from any source, a battery charger, inverter charger, solar panels, or even another engine’s alternator if the two are paralleled, which is connected to the same battery as the engine/alternator. 

While on the subject of alternators, their temperature should be measured using your IR gun, or a permanently-installed probe associated with a vessel monitoring system, or the wired remote probe from a digital thermometer. The hottest portion of an alternator is usually the stator, essentially the center of the barrel-shaped portion. Squeeze the IR gun’s trigger and while doing so wave it over the entire body of the alternator, while holding it as close to the alternator as possible (again, be mindful of moving belts, pulleys and the fan). This scan feature will yield the highest temperature.

While it varies from manufacturer to manufacturer, typically, large frame, high output alternators designed for continuous duty can endure temperatures as high as 300°F (149°C) for short periods, and up to 240°F (116°C) for longer stints.

Belts: If visible, carefully eyeball your belts, idlers, sheaves and tensioners, as well as the area directly below the front of the engine, for generation of excessive dust. The only way to know if your belts are generating dust is to keep the front of the engine clean. If it’s caked with years’ worth of accumulated belt detritus, and oil, you’ll have no way of knowing if this the legacy of a since corrected problem, or if it’s newly generated. The belt analysis is best conducted at rest.

Exhaust: The engine’s dry exhaust system, the portion between the engine’s exhaust manifold or turbocharger and seawater injection point (or the whole accessible run if it’s a dry exhaust vessel), should be monitored using your IR pyrometer. Beware, while IR pyrometers are generally accurate, they can be fooled by highly reflective surfaces like polished stainless steel, chrome and foil-faced insulation; the latter is commonly used on dry exhaust systems. In that case, areas where you intend to measure can be painted with flat black paint, or black tape can be applied, a small square is all that’s necessary. American Boat & Yacht Council (ABYC) Standards mandate that if your measurements exceed 200°F (93°C), on any portion of the exhaust system you can touch, they are too hot; they must either be insulated more effectively, or guarded to prevent contact.

Be sure to check the turbo-charger; “dry,” non-liquid cooled turbos must be insulated, as well as the flange between turbo and exhaust riser. In many cases it is entirely exposed. I’ve measured some of these at more than 500°F (260°C).

As a side note, even if adequately insulated, an underperforming engine room ventilation system can lead to overly hot dry exhaust surface temperatures. The reason for this phenomenon; if there is insufficient air turnover, then heat cannot be carried away from these surfaces rapidly enough to maintain the required sub-200°F (93°C) temperature.

From here move on to the wet portion of the exhaust system. Measure the hose immediately after the mixing elbow, especially on the top or 12 o’clock position, as that’s likely to be hottest. Counterintuitively, the highest temperature may be reached at lower speeds, idling even, when less water is being injected into the exhaust system. Again, no portion of the wet exhaust system should exceed 200°F (93°C); typically, it’s closer to 130°F (54°C). One of the more popular wet exhaust temperature alarms, an indispensable component on any inboard-powered vessel, triggers at 165°F (74°C). 

In part two, we’ll continue to look at the importance of temperatures as well as fuel filters and running gear. 

By Steve D’Antonio

Beginning his career in 1988, as a marine mechanic, electrician, manager and partner of a custom boat building shop and two boatyards and technical journalist, as well as through Steve D'Antonio Marine Consulting, Inc, Steve provides personalized and hands-on service to boat buyers, boat owners, boat builders and equipment manufacturers, as well as others in the marine industry around the world. Steve is an American Boat and Yacht Council Certified Diesel, Electrical, Corrosion and Systems Master Technician/Adviser. To learn more or to contact Steve, go to stevedmarineconsulting.com/.