This is much more than a rare and hypothetical “what if?”-scenario: I remember a handover last year at the Lake of Constance. After the sea trials with some lush hours outside sailing, we returned with a happy boat and happy clients to the pontoon. The couple berthed their brand-new boat with much caution and safely. After all lines had been tied up and the boat was secured, I started to pack the mainsail in its lazy bag and the skipper turned off the engine. Well … he tried to turn it off.

What if “Stop” doesn´t work?

For whatever reason the “Stop”-button which normally makes the Diesel die down did not work. Nothing happened, the engine just continued to rattle on in idle. Of course the reason for this was a malfunction within the control panel and repairing it was a no-brainer, but still: The Diesel kept on running and the question arose how to stop it.

Shutting down a compression ignition engine

First of all, killing the main battery switches, which was the first impulse of my customers, won´t bring anything. The engine battery is only needed to run the starter. A Diesel engine works completely without electric energy – killing the battery and turning off the boat won´t change a thing. That is because a Diesel is a so-called “compression ignition engine”. That is why a Diesel does not need spark plugs. The fuel-air-mixture is ignited by the compression of the piston and the high temperatures that arise when the pressure through compression is so high.

Can you spot the kill switch?

That is why a Diesel will run indefinitely, theoretically. So, what do you do when this happens to you? The solution is simple: Any modern Diesel boat engine will have an emergency shutdown switch. This is something you should ask your dealer or look for in the owner´s manuals of your new boat. In the said Oceanis 30.1 which has a 21 horse power Yanmar engine (and similarly all bigger engines as well) the kill switch is situated right behind the engine. It´s not easy to reach, I guess this strange location is a safety precaution to prevent accidental pushing, maybe it is this because there is the only location to put it. In our 30.1 you will have to enter the bathroom and kneel down.

Emergency shutdown at Yanmar

The side maintenance hatch is to open and you will see a large rubber made knob. Caution! In case this scenario takes place, the engine will be running, vibrating, moving parts and extreme heat can cause severe injury, bruises and burns! So, best is to have a small light and carefully press the button. What happens is that a valve will open and the engine will suck air. This kills the pressure inside, no high temperature can be maintained needed to ignite the aerosol of fuel and the engine will be shut off in a matter of seconds. Easy.

Yanmar and Volvo-Penta systems for kill switches

I remember the old MD-11 engine on my first boat. This engine had a kill switch in form of a bowden cable in the cockpit which was the usual and ordinary way to switch it off. Panels like the modern one shown in my first pictures had not been invented yet. But this MD-11 was a Volvo-Penta and since I decided to go for the Swedish brand in my own new boat as well I was interested to see the current system as well.

How to stop these big bastards?

Lucky me we have a Gran Turismo 45 power boat in our shipyard, so I climbed into her big engine room. Two massive Volvo-Penta D6 Diesel engines are the powerhouses propelling this yacht to planning speeds. So, what happens if for some reason these big blocks won´t turn off?

The Volvo Penta kill switch

Volvo-Penta has a clear red turn switch that acts as the emergency shutdown device. This is mounted (at least on this yacht) right in front of the engine and thus very good accessible. So no hazard to your fingers to get sucked into the drive belt or stunts like this. I take this experience as an inspiration to check my own new little D1 engine for the Omega 42 where the kill switch is mounted and how good accessible it will be when the engine is finally put into the boat. Definitely a separate article for my #buildingreport series.

Alternative methods to switch off the Diesel engine

Of course there are alternative methods of killing a Diesel engine. Maybe you don´t know where the kill-switch is installed or for some reason it is inaccessible. As I mentioned earlier in this article a compression ignition engine won´t go out until the fuel is consumed fully, the logical reaction and alternative is to interrupt and shut down the fuel flow.

Close the valves!

Any boat has at least one of those fuel valves and there are two principal locations. First location is the immediate surroundings of the fuel tank. For example in the Oceanis 30.1 the fuel tank is in the large locker, a small cap in the floor reveals the valve. Closing it will deny the engine fresh fuel in a matter of maybe half a minute, then the pipes are sucked empty and the engine will finally die.

Role model: Power boats

The D6 also have those valves near the engine, so that´s a double feat. Also, up there at the steering station between Captain´s chair and guest chair, a little valve panel is installed. In case of emergency you don´t have to jump down into the hot and loud engine room: Bowden cables will shut down fuel flow right from the steering. There´s also a fire suppression system that can be activated when shit has really hit the fan. Similar systems can be found in high-price sailing boat brands as well: For production boats this is the future when it comes to safety. Anyways, I hope that this article does have some information value – stay safe!


You might as well find interesting to read:

Yanmar or Volvo-Penta for my new boat?

Smashing a catamaran emergency escape hatch

Thinking about the safety concept for a sailboat