*The Diesel Doctor* Stop What You Started

How to stop a runaway diesel

You've backed into your slip without incident, the lines are secured to the pilings, and you're ready to shut down and head for the Tiki bar. You push the stop buttons, but the big diesels in your engine room keep on chugging. In fact, they start roaring louder - and faster. Next thing you know, a huge cloud of black smoke is billowing from the boat. By the time you get things under control, there's a crowd of onlookers gathered and every seat in the bar is covered in oily, black soot. You've just had an encounter with a runaway diesel.

What exactly happens during a runaway?

Basically, an out-of-control diesel can't be shut down by traditional means when a combustible material - usually oil escaping from another part of the engine - gets sucked into the air intake. Common causes of runaways are turbocharger or supercharger seals that have gone bad, an overfilled crankcase spraying oil out of the breather, or an external source of flammable gas or liquid. If, for example, your genset fuel line ruptured near the diesel's intake, you could be in for a runaway. Stopping a runaway is fairly simple-just cut off the engine's air supply. Of course, when black smoke is billowing all around you, the diesel is roaring at full volume, and you're trying to back into a slip, this is easier said than done. But these runaway - taming tricks should help you get everything back in order.

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 intake. ****

3. If it's an emergency situation, use your washdown hose to flood the intake with water (be aware, however, this may cause additional damage to your engine).