Zen & the Art of Marine Diesel Maintenance

After forty plus years as a marine columnist, I must admit that I still get a sadist thrill out of poking fun at powerboaters. I mean—if we inkslinging stickboaters can’t berate stinkpotters, what good is the literary life? However, there is one thing (besides spending money) that marine motorheads do better than ragmen and that is maintaining their inboard diesel. 

Sailboaters have a tendency to pray—which isn’t terribly effective. 

“If it’s not broken, don’t fix it,” is a good idea. But the concept is carried too far if it results in “If it’s about to break in safe harbor, ignore it so it can break at sea and put you, your crew, and your vessel at risk.” 

First off, I should tell you that I do not consider myself much of a mechanic. However, my lifelong poverty has compelled me to tear apart many an engine—enough of them to confidently state that putting them back together is the hard part! (Especially if you are anal and want to use the same number of parts.)

One good way of thinking about marine diesel maintenance is in terms of problem-solving. Life is full of problems—how to snuggle up to the opposite sex, how to manage to be in the barroom’s toilet when the check arrives, how to fib to the taxman, etc. 

A successful businessman is just a problem-solver with an easy way to keep score. And here’s the bottom line on diesel maintenance: Your engine will run many years far more reliably and cheaply if you do just a few simple things. 

Here are those things. 

One: Read the manual. I recently purchased (seven blissful years ago) a new Perkins M92B from Parts and Power in Tortola. I not only read the manual, I purchased a digital parts list and the rebuild manual as well. 

Two: Talk to the peeps who, day in and day out, work on these engines. Nothing is perfect. Chances are, all the stuff that’s gonna happen to your engine has already happened to its brothers and sisters—and their ‘diesel doc’ knows. Ask. 

Three: Before you crank up a diesel, check its fluids—especially its lubricating oil. Most boaters don’t do this saying—“Hey, I don’t get under the hood of my car each time I turn the key—shouldn’t my marine diesel be even more dependable?” I repeat: check your oil every time. 

Four: Once the engine cranks up, watch the exhaust for a couple of minutes to make sure that you have cooling water and to observe the quality of its flow.

Note: the exhaust gas should be clear once the engine is up to temperature in the Caribbean—white, constant black, and intermittent black smoke during acceleration all point to different problems.

Fatty isn't the only Goodlander interested in diesels
Fatty isn’t the only Goodlander interested in diesels

There are only two common things that happen to a modern diesel that will ruin them forever—running them without oil or running them too hot. You CAN NOT do this. Ever. For any reason. One second is too long. If you have no oil pressure or the engine is too hot, shut it down instantly. Any thought of “I’m only three seconds from my dock!” is an expensive one. 

Now the reason that you HAVE to do #3 and #4 each time is to get in sync with your engine. And the best way to do that is to use your five senses. When you check your oil—really look at it. The level is important, sure, but the rate that it is burning oil is important, too. For instance, if your engine starts using more oil and its exhaust starts smoking at the same time—two important elements are clearly telling you that you have a developing major problem. Engines don’t lie. They don’t exaggerate. They always tell the truth. And 99% percent of the time, they will begin telling you the truth long before there’s a major, time-consuming, expensive problem. Thus, cruisers with limited budgets have no choice but to be more proactive maintenance-wise than their wealthier counterparts. 

Back to #3: look at the oil. If it looks like honey, great. The blacker it is (assuming proper oil and filter changes), the more micro bits of metal, salt, and abrasives are floating within. If it is suddenly black, why? Any sudden change should be noted—and highly suspect. Touch the dipstick with your thumb and forefinger to take a sample—and rub them together. Good oil, as mentioned, is smooth as honey. If suddenly your oil feels gritty or sandy—that’s a major clue disaster awaits. 

Yes, you can send it off to a scientific lab for a fuller, most costly analysis—but this is the first step. 

If your oil level ever rises—yes, I’ve had this happen—something bad is leaking into your crankcase. If your oil looks milky—that’s usually water leaking in through the cooling system via a head gasket, heat exchanger (check zinc), or oil cooler. 

Any engine change should be noted and considered—a change in sound, for example. Or odor. (Rubber smells as temperature increases.)

Here’s a sad but important truth: engines don’t fix themselves. 

The fifth thing I want you to do is widen the aperture of your view to include your engine compartment, engine beds, and bilges. Example: Check the walls of your compartment in the fore area of the engine in both natural and bright artificial light. You might find an area of shading in one area in a circle around the front of your engine. This is the bits of rubber being thrown from your ever-wearing fan belt. While some wear is normal, if this wear appears to accelerate, immediately replace your belt(s). 

Check the engine beds as well. Is one of your engine mounts corroding faster than the other? If so, why? On the engine itself, look for staining, rusting, and/or corroding. Gaskets often fail a molecule at a time, and it is far better/cheaper to fix the problem now, before the engine overheats, than later. 

If you are on a monohull with an amidship cockpit and you sail offshore—your engine will be getting wet from above via your steering pedestal leaks. This can be a vexing problem. I have a plywood watershed under my pedestal to shunt water into the bilge rather than pool on my engine, which has dissimilar metals and electro components. 

Once a month, I wipe down my engine and trany (always feel under the trany for rear-seal leaks due to misalignment) with an oily rag to get in sync with them. Modern diesels will practically run forever—if their owners gives them a bit of love and attention. (end) Editor’s note: the Goodlanders just spend six months in NZ and three in New Caledonia—and are currently entering the Torres Straits. 

Cap'n Fatty Goodlander
Cap’n Fatty Goodlander has lived aboard for 53 of his 60 years, and has circumnavigated twice. He is the author of Chasing the Horizon and numerous other marine books. His latest, Buy, Outfit, and Sail is out now. Visit: fattygoodlander.com