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post #1 of Old 07-19-2004 Thread Starter
Ben Hilke
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Runaway Diesel Engine

The relative quiet of the marina suddenly gave way to the alarming sound of an engine revving well beyond safe levels of rpms and decibels.
The horrifying look on my dog's face said it all. Something had just gone very wrong—not your normal everyday kind of wrong—but the kind of wrong that etches into memory and loosens your bowels in the same moment. The noise was paralyzing and as my eyes met Beau's in one of those dreadful moments where time becomes a record played too slowly, he was communicating clearly in a telepathic way. His big blockhead was looking at right me saying, "Nice one; what the hell did you do now? And why are you just standing there? I'd be running away very fast right now, but I need your sorry ass to get me off of this boat. OK, this noise is starting to really hurt, please do something, anything, and when this is all over with, I better get one hell of a good treat for being supportive."

As I looked into his eyes, my mind was saying, "Beaureguard, we're in real trouble here. I know I say that often, but I mean it this time. Why in God's name did He not give you opposable thumbs so that you could grab a screwdriver right now? Please tell me that for some unknown reason you know how to shut down this crazed, sociopathic, runaway diesel." Of course he didn't have the answer, the worthless mutt, and it occurred to me that I was going to have to confront this mechanical nightmare on my own.

A little background might help explain how we ended up in this horror with my 25-hp inboard racing at 5,000 rpms while the boat remained tied securely to the dock. The buildup had all started so simply. Two months before I was doing my typical once-every-two-week engine check when I noticed milky oil on the dipstick and realized that water was somehow entering the motor. Since the only way that water can leak into my engine is through the water pump seals, a cracked head gasket, or a hole in one of the cooling jackets inside the block, I hoped it was the water pump. The other two options would mean a serious engine overhaul or a new engine. So I ordered a water pump and waited a few weeks for delivery.

Regular maintainance is an imperative for the boat's power plant, and as the author learned, procrastination has a vicious bite.
During the interim, the engine sat with water in the oil. I can tell you now that this is not a good idea. When I finally got the new water pump, I replaced it no problem and ran the engine to heat the watery oil up. Amazingly, it ran fine. Like a kid who just escaped with the cookie jar, I felt happy that I got away with letting the engine sit so long. So I later changed the oil and filter and ran the engine again. The oil was still a little milky, but much better than before, which led me to believe that it was the water pump—good news all around. Because I was hurting for time, I decided to wait a week to run it again and do another oil change. Simply put, that was my second stupid decision. Just because you get away with one bad move doesn't mean you should try it again. Unfortunately that week turned into two and that's when it started to get interesting.

When I finally got around to it, I turned everything on to fire up the old girl and then turned the key. I had the engine in neutral with the throttle at about three-quarters just to get her started. She cranked, but didn't start and sounded sluggish. So I tried it again and let it crank a little longer. This time she fired up and began to gain rpms as the fuel started to flow. So I cut back the throttle, expecting the engine to settle into her normal chugging sound. But expecting normalcy at this point was like going away for the weekend with your buddies and then coming home, sitting in front of the TV, and expecting your spouse to serve you dinner. Like any spouse, the old inboard had other ideas. She was tired of being ignored and mistreated. The engine had finally had enough and it was time to teach her old man a lesson. Scorned lovers tend to be dangerous and vindictive. Sometimes they'll grab a gun or a knife, or a rolling pin and try to kill you. This one decided to go full throttle out of control and threaten me with exploding cylinder heads if I didn't shape up and fix the problem and fast!

"With the noise reaching a deafening whine and my brain spinning into high gear, my first impulse was to turn off the key, but doing that didn't change anything. What could I do?"
With the noise reaching a deafening whine and my brain spinning, my first impulse was to turn off the key, but doing that didn't change anything. Runaway gas engines are easy to solve, you just turn off the key, thus killing the spark and shutting the motor down. But this was a diesel engine, not gas. So next I pulled the fuel shutoff. Nothing. (I later discovered this was due to a stuck internal throttle mechanism.) Miraculously my brain began to comprehend what was occurring. I reached down to the throttle assembly attached to the engine (not yet aware that it was stuck internally) and tried to free it with my bare hands. As I tugged on the throttle, I smelled something burning and quickly realized that my hand was being roasted by the exhaust pipe that runs next to the throttle. I have heard that third degree burn victims say they don't feel any pain because the burn is so severe that the nerves are killed instantly. Though I never intended to prove that theory correct, it turns out that these folks are right. I quickly yanked my hand back and looked at it. That's gonna hurt I told myself, but first I needed to shut that engine down.

The good thing about diesels is that they're simple, three things make them run: fuel, compression, and air. Air, that was it! I needed to shut off the air supply. At this point it seemed like I was jumping into a war zone. Experienced mechanics have since told me it was stupid and dangerous to climb into the engine compartment with a runaway diesel because when the first piston decides to blow through the head, it can be the equivalent of a land mine going off. But love does funny things; just watch an episode of Jerry Springer some afternoon and that will become clear. So there I sat, on top of a screaming engine trying to figure out how to shut the air off. Shutting down two of the cylinders would be easy. I could put one hand over one intake and one over the other, but I have a three-cylinder engine with three separate air intakes. I needed another hand, but when I looked at Beau for assistance, he just looked back defiantly—worthless cur, why do I even feed him. The only solution was to use my foot to cover the third cylinder intake, so I pulled a groin muscle achieving a position even a yogi would admire, and the motor slowly stuttered and then came to a silent halt.

Marina life for the author and Beauregard aboard their Westsail 32 is ordinarily a lot less frenetic.
I clambered out of the engine compartment and limped over to a berth and sat down, breathing heavily. With my ears ringing from the deafening noise and my hand beginning to blister into a truly ugly wound, I thought about how my day had just changed. The sky seemed a little bluer, the sun brighter. Through the buzzing in my head I heard my neighbor, a police officer, hailing from the dock, asking me what happened and was I was still alive? After climbing aboard, he peered down through the companionway to take a look for himself.

"Just a little domestic dispute; I've got her calmed down now," I managed. He looked at me confused. I smiled and he smiled back, and then I began to tell him the whole story. After recounting the tale and finding some burn cream, he told me that he wouldn't have known what to do, and that I was a quick thinker. I laughed knowing that if I were smart I wouldn't have had to solve the emergency in the first place.

So that brings me to the lessons of this story. First and foremost, treat your engine right and always make enough time to spend with it. Second, plan ahead for the worst and have an emergency engine shutdown plan. The third and final lesson is that if you're working on an engine and find yourself asking a dog for help, don't count on any assistance. He may be man's best friend, but that doesn't include engine emergencies.

Runaway Shutdown Tips

Admittedly, having an inboard engine rev out of control is an anomaly in the world of maritime experiences. However, should you ever find yourself in the same situation, you'll want to keep in mind the following steps.

1. Aim a carbon dioxide fire extinguisher at the air intake, and blast away.
2. Stuff a blanket, throw pillow, or life jacket over the intakes.
3. As a last resort, use your wash-down hose to flood the intake with water. (Be aware, however, this will probably cause additional damage to your engine.)
4. If shutting off the air isn't an option, create a fuel shut-off valve close to the fuel intake so that the engine will run out of diesel quickly. (Just remember the engine will need priming before it can be started again after taking this measure.)

Detroit Diesels have an air cutoff butterfly valve as standard equipment, but for other engines you can buy a butterfly air shutoff and install a Morse or Teleflex cable to it and run the cable to the helm station. Make sure that the butterfly valve is sized for your size engine.

Last edited by administrator; 10-07-2008 at 04:31 PM.
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