BMB Stop Switch

[Nasher]

Hi all

I'm putting a little BMB Mariner engine into a boat I'm restoring and could do with a little advise.

I've downloaded an original service manual for the engine and the recommended way of stopping it is by turning off the fuel tap and letting it run out of fuel.

In my installation there is no gearbox as such or clutch, the output shaft is permanently connected to the prop shaft. The original was designed like this and I don't want to change it. Of course this means the prop is turning all the time the engine is running out of fuel, which might take some time.

I can reach the choke lever easily, which could stop a warm engine, but I'd like to add in a hidden switch to ground the Magneto and cut the sparks.

From the image below, could anyone suggest what I should be grounding?

Thanks

Nasher.

 

[William_H]

The points are a contact between magneto coil primary and ground. Almost certainly in your photo the yellow wire going to green wire is the one to the magneto coil primary. If you ground that wire you should stop the engine fairly convincingly. I imagine this might be a 2 stroke engine with oil in the fuel. The theory of running it out of fuel is to dry the carburetor. If this is not done the petrol can evaporate over time leaving just the oil to foul up the first start on your next voyage. If the carb bowl has a drain point this could be used to have the same effect. Or just try the engine and see if oil in the carb is a problem after a lay up. good luck olewill

 

[Nasher]

William, many thanks for your suggestion, I'll run a temporary wire through the base plate and try grounding it on the block when I get the engine running.

You are correct, it's a two stroke, and the recommended Fuel/Oil mix is quite heavy at 24/1, but that's not unusual for a 1940/50s engine. I hadn't considered the possibility of the float chamber ending up with a heavier mix after a layup, so will watch that one.

Nasher