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Marine Diesel Engine Advice from a Pro

Powerful Questions

We interrogate a long-time diesel mechanic with some quirky, but rather basic, queries about diesel engines.

I’ve known John Hice, the head honcho of Panama City, Florida’s Gulf Coast Marine Service, Inc., for years. I first met Hice, I guess, when some highly-skilled expertise was needed to improve the health of my 4-kilowatt Onan generator, a device that, like most of its kind, does not see the usage it should and therefore suffers gravely, i.e., expensively. Of course, I have never claimed to be a diesel mechanic—or anything close to it—so since my first meeting with Hice more than a decade ago, I’ve built up a telephone-based friendship with him that gets periodically rejuvenated every time I have an issue with or question about my diesel engine or somebody else’s.

John Hice of Gulf Coast Marine Service in Panama City
When we’re stumped by our marine diesel engines, John Hice of Gulf Coast Marine Service in Panama City, Florida, is the go-to resource for answers.

What happened over the course of a few recent telephone calls was a little special, though. After arguing good-naturedly with a dear friend about a diesel-related matter and then calling Hice to resolve things (in my favor, as it turned out ... Ha!), I was struck by a veritable brainstorm. Why not put in a little serious thought and come up with four or five niggling questions I’ve always had about diesel engines (and maybe that you’ve had, too), and put them to Hice? Then, after giving him a few days to prepare his always reliable pronouncements (I mean, the guy’s been working on diesel engines for almost 40 years now), go ahead and compile the results for the readers of Power & Motoryacht. So here we go—the results!

Ether, Yes Or No?

Years ago, if memory serves, the use of ether in spray cans to start cold or otherwise recalcitrant diesel engines was both common and commonly accepted. Indeed, Detroit Diesel actually once offered two-stroke diesels specifically outfitted for cold climates with auxiliary components that would administer a shot of the highly combustible anesthetic in hard-to-start situations. Which begs the question today: Is it really okay to use ether—maybe just a smidge—to crank a cold or much neglected diesel engine?

“Not advisable,” says Hice, by way of launching some serious gloominess. Turns out that ether has a very low flash point compared to diesel fuel. So, when you spray the stuff into the breather of a diesel engine and it makes its merry way into the cylinders, some exceptionally disruptive, decidedly premature detonation is likely to occur. A very controlled explosion that should be taking place when the piston is at about top dead center, instead takes place when the piston is only one third of the way there, or even half of the way. This totally discombobulates the general coordination of virtually all the engine’s major rotating parts, possibly damaging piston rods, rings, ring lands, cylinder walls, and any number of other expensive components. “And engines today have a higher compression ratio than the cast-iron dinosaurs and two-cycle beasts of old,” adds Hice. “Some also incorporate ‘air heaters’ in the intake system that would most likely ignite the ether before it even got to the combustion chamber and that would make it likely you’d do even more damage and quite possibly bring about personal injury. I repeat. Do not spray ether down a modern diesel’s throat!”

Check When Hot?

Why do the dipstick instructions for one marine transmission specify checking fluid levels prior to a regular cold start but for another transmission specify: CHECK WHEN HOT? “The difference depends on the manufacturer,” says Hice, “and how that manufacturer is selling his units.” In most cases, he continues, a manufacturer will know for certain the exact capacities of all the related components—the transmission oil cooler, oil filter, hoses, and everything else that’s involved. So, since he’s in control of these known capacities, it’s possible for him to determine (and mark on a dipstick, at ambient temperatures) precisely how much transmission fluid is required to do the job. “But then there are other manufacturers who sell transmissions but don’t have any idea where they are going or how they are going to be configured,” Hice concludes. “And because they can’t accurately predict how much fluid a system will actually need to run right—after all, they don’t really know what sort of components and capacities will eventually be involved—they mark their dipsticks: CHECK WHEN HOT. That addresses the issue.”

Lehman diesel engine
Inspect engine hoses regularly, and, when one needs replacing, don’t recycle hose clamps.

What About Those Hoses?

Marine hoses are tricky, says Hice—it’s tough to know when one’s about to fail. Indeed, Hice says he’s dealt with big exhaust hoses over the years that looked fine on the outside but were delaminating inside, causing backpressure and other engine performance issues. When should you replace the hose or hoses on your diesel engine? “Every eight to ten years,” affirms Hice, “unless the engine has undergone an extremely high temperature overheating situation or you see cracks or rust emanating from the wire inside a hose or hoses, in which case you should do something immediately.” Hice offers another piece of advice that’s almost bound to be short-term expensive but comparatively economical in the long run: “When changing one hose—change all the rest,” he states flatly. “And don’t forget the hose clamps.” Hose clamps? According to Hice, engine hoses (and the clamps that hold them in place) expand and contract almost constantly, a scenario that produces metal fatigue, especially in cheap, low-grade stainless steel. “Don’t spend hundreds of dollars on new hoses,” he advises, “and then blow it all for the sake of a burnt-out $1.10 hose clamp.”

You’re kiddin’—Every Month?

Most any dedicated boatnut has kept his pride and joy in a variety of marinas and locations over the years—it’s just one of those facts of marinized life I guess. And undoubtedly, said boatnut has also experienced, over the years, long blissful periods when his engine zincs lasted as if they were blessed by the universe, but other times when they seemed to dissolve like Alka-Seltzer in mere weeks. Why? Are the latter circumstances related to the former? “Heck yes,” says Hice. “The amount of time your engine zincs are going to last is very dependent upon where you keep your boat and the environment that immediately surrounds it, no matter how well you think you’ve got her galvanically protected.” Hice’s Gulf Coast Marine Service manages several vessels in the Panama City area and he says that engine zincs last for two or three months on some and a year or more on others. He cites broken, or shorted-out electrical lines under docks of marinas as one culprit and poorly zinced neighboring boats as another. “So since you’re never going to know exactly when things will change galvanically or why,” he adds, “you should check your engine zincs at least once a month, even if you typically get a lot of time out of them. You never know.”

Genset Blues! Run!

gensetI hope that by making the statement I am about to make I will not bring the wrath of the genset gods down upon me. But hey, over the past decade or so, I have never had any trouble with my main engine—none whatsoever. But my genset! That humble little 4-kilowatt Onan has cost me a humble little fortune, considering what I’ve spent on refurbished injectors, water-pump replacements, cooling-system rehabs, new hoses, and any number of other extravaganzas. But the problem at the bottom of these dreary carryings-on, according to Hice, is simple. “Bill,” he says, “you just don’t run your genset enough. You should crank it up and let her rip—under load for, say, 20 minutes or half an hour—every time you crank the main engine, whether you take your boat out or not.” The list of evils Hice predicts for an underemployed genset is truly frightening, especially from the financial perspective. Salt-laden air can corrode the windings of the generator unit itself and sneak into the cylinders of the engine too, bringing rust to cylinder walls and piston rings. Salt-laden moisture will build up in the oil as well, wreaking all kinds of acidic havoc. And fuel may turn to shellac or gum in or around the injectors. “Which is just about the worst of the whole bunch of problems,” opines Hice ruefully. “I mean, if you use your generator so infrequently that you gum up the injectors, why the heck have a generator in the first place? I mean, really!”

This article originally appeared in the February 2014 issue of Power & Motoryacht magazine.

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