Electronic engine stop

I am working on a boat safety device, aimed particularly at single-handed fishermen, but with application in other areas too.

The basic principle is if the crewman falls overboard, an alarm sounds and the engine stops - so he doesn't have too far to swim to regain the boat. I know that's a simple description, but I hope it gives the general idea.

My problem is that there are many marine engines in current use. So it would speed up my research if forum members could explain to me how to stop current engine models. I understand that, in most cases, a solenoid is used to stop/enable fuel injection. I need to know:

1. The typical current consumption of the solenoid (figures I have been given look like starter current, rather than running current!)
   
   Typical wiring schematics

Many thanks,
Mike.

 

There are 2 types. the old type is a solenoid that enrgises a magnetic piston that pulls on the stop lever pulling the rack back to zero fuel. These I have made from starter motor pre engage solenoids. They draw approx 15 amps ( quite a lot but is momentary)

The moder type is an electric valve on the fuel delivery pump it has to be energised to run or no fuel. When I leave my diesel truck any where I disable the engine by removing the fuse and put it in the glove compartment --the engine will not start.

These are much less ampage as they are constanty energised.

The even more modern common rail engines will be similar.

 

Hello Jack, thanks for this.

My relays are rated at 15A, 24V so should cope with your worst case. Also, I have both normally open and normally closed circuits so will handle both the modes you describe.

Does anyone know of an engine that needs more than 15A to stop it?

I can get a 40A relay, but it is bigger so I will need a bigger case to fit the unit in. I don't want to do this unless I need to.

 

The Murphy Gage folks have a stop solenoid that is armed by hand, set by pulling hard on a T handle.

The unit only requires a tiny amount of juice to pull a pin , and the spring pulls the rack on the diesel to STOP.

AS a system , they use a Hot Shot battery , so it will operate even if the boats electric system is out.

FF