Modern marine diesels are amazingly dependable—but not fool-proof, not idiot-proof. I know this. I’ve learned it the hard way. This idiot has injured a number of ‘em. Being a klutz around a marine engine can be very, very expensive. Here’s how to avoid needless repairs.
First, an overview.
The #1 cause of premature marine diesel failure is exhaust-related.
The #1 cause of premature marine diesel failure is exhaust-related. The engine gets salt water inside the combustion chamber, and the engine fails. The #2 problem is light-loading. The engine is run solely to charge batteries or refrigeration. It never really gets up-to-temperature. Thus, the cylinder walls glaze and compression decreases. The #3 problem is simple lack of use. Diesels like to be run hard. They don’t need to be pampered if they are properly maintained.
Most minor marine diesel problems are fuel-related. You must feed your diesel clean, waterless fuel if you want it to run dependably.
The first thing I did after buying my current 43-foot ketch Ganesh was to empty and hand-clean its diesel tanks. Next, I refilled those tanks to the brim with clean diesel fuel, and treated that fuel with Biobor, so no bugs would grow in it. (This is extremely important in the tropics; we use Biobor each time.) I also installed a Racor filter with a 30-micron element as a primary filter, and used the engine-recommended canister filter as the secondary. All marine engines need these two filters at all times. Just to gild the lily, I have a water-sensor alarm on my Racor filter and also a suction gauge so I can monitor the state of my filters. Yes, I try to keep my tanks topped up to prevent interior tank condensation. No, I don’t use bio-diesel (smells like popcorn) because it attracts more moisture more than regular diesel. (See “Dealing With Dirty Fuel” p. 38.)
Everyone knows you need strong batteries to crank a diesel—but few realize that battery cables decay, corrode, and absorb moisture until they are almost useless. These cables should be marine-grade, silvered, and much thicker than you think. Not only is the size of the engine and batteries part of the equation, so is the distance run (including routing, switches, etc.). I’ve had engines with new batteries that barely cranked with the existing cables—and yet spun very fast with new cables.
How you use your engine is important, too. I rarely idle mine for long periods. If possible, I put it in gear at the dock. If I have to wait for bridge or something, I allow it to run in neutral between 1000 and 1200 rpm to prevent excessive vibration. I always idle down before shifting into forward. I never increase or decrease throttle rapidly. Instead, I do so smoothly and over a few minutes—much easier on the transmission and mounts.
There are only two things you can do to ruin a diesel permanently—and that’s to run it hot or without oil. Both are alarmed on my Perkins engine. I regularly flush the fresh water side of my coolant system and have the heat exchanger ‘boiled’ with acid every five years to remove scale. (You can’t see this scale but it is there—and very detrimental.) I use ELC (Extended Life Coolant) and change it every three years. I also check my impeller once a year—and carry a spare raw water pump faceplate and bearings offshore.)
I always change my oil and filter exactly as recommended by Perkins or once a year. (If I am going to leave my boat for a couple of months, I change the oil before I go to minimize moisture.)
Ditto my air cleaner, transmission fluid, and filter. While running, I try to vary my RPMs once an hour—and run it at max cruising RPM for ten minutes twice a day. (This prevents the oil from sludging and inhibits cylinder wall glazing.)
I religiously follow all the engine manufacturer’s instructions—including the section on zincs and electrical grounding/bonding. Modern engines have more and more aluminum parts—a huge potential danger to us sailor-types.
I keep an engine log and my wife and I attempt to get ‘in-tune’ with our engine by regularly wiping it down, etc. Yes, we check our fluids each time before cranking.
Which brings us back to the exhaust system—the Achilles heel of most marine engine installations. Since we regularly sail in the Indian Ocean and the Roaring Forties, we have a specialized ‘offshore sailor’ exhaust. This consists of an additional gizmo called a water and exhaust separator—which results in an ‘exhaust gas only’ output above the waterline and a water-only exhaust output in two places, one on each side of the hull.
Thus, it is almost impossible for wave action and/or angle of heel to allow water to back up into the engine because once it re-enters the exhaust separator, the water leaves by gravity and can’t get up into the exhaust above. (Even if some drops did, they would immediately get trapped in the Aqualift.)
Thus, this system has two well-engineered gates that prevent saltwater from backing up into the engine, unlike 99% of the vessels in the world.
Wait, we’re not done: this leaves a little bit of water in the Aqualift water trap muffler. There’s a drain hole in this muffler that allows you to drain it in the winter to prevent freezing. I’ve replaced this plug with a valve. Thus, if I’m heaving-to in extreme weather and/or worried about heeling more than 90 degrees, rolling, or pitch-poling, I take a couple of minutes and drain all saltwater from my exhaust system—every drop. Thus, even during repeated 360 rolls, I should have a dry exhaust.
Excessive? Perhaps. Maybe. Probably. But such attention to detail is why I’ve been able to circumnavigate so many times without major mechanical mishap.
I am extremely proactive when it comes to practicing traditional seamanship. It isn’t enough for me to prepare for what I think will happen—I need to be prepared for what might happen as well.
One more hint: this ‘getting in tune’ with your engine sounds a tad new-agey but isn’t. Your engine and your rig probably will never do anything naughty without sending you a memo first. However, in order to receive this memo, you have to look and listen repeatedly to the status quo in order to be able to hear or see the obvious change.
Recently, I noticed a tiny bit of rust on my port forward engine mount—which enabled me to order a new raw water pump seal and bearing long before its inevitable failure. Excessive ‘black dirt?’ Check your belts. Damp under your transmission? Check your rear transmission seal. Green battery lugs on your starter motor? Do something, mon, do something!
My coolant overflow hose doesn’t go into the bilge, it goes into a bottle so I can monitor any changes in color, suspended particles, petroleum sheen, etc.
In essence, I ‘keep my eye’ on my diesel—and this allows me to be a spaced-out, blissed-out hippy without a care in the world as I endlessly circumnavigate.
Editor’s note: Cap’n Fatty and Carolyn are currently massaging their Perkins diesel in the Indian Ocean.
Cap’n Fatty Goodlander and his wife Carolyn are currently on their third circumnavigation. Fatty is the author of Chasing the Horizon and numerous other marine books. His latest, Storm Proofing your Boat, Gear, and Crew, is out now. Visit: fattygoodlander.com