Helena Frye
A mercury switch is an electrical switch that opens and closes a circuit when a small amount of liquid metal mercury connects metal electrodes to close the circuit. It is a type of kill switch that prevents accidental starting of the motor and shuts the motor down if the motor pops out of the water, preventing over-revving. This is achieved when the engine is tilted to a certain angle, which makes the switch make and kills the engine.
| Characteristics | Values |
|---|---|
| Purpose | To prevent accidental starting of the motor and to shut the motor down if the motor pops out of the water |
| How it works | When the boat is tilted too much, the mercury inside the switch connects metal electrodes to close the circuit and ground out the ignition, killing the motor |
| Design | There are several different basic designs (tilt, displacement, radial, etc.) but they all share the common design strength of non-eroding switch contacts |
| Installation | The switch should be installed at a specific orientation, with a "slot" or hole on the body of the switch that corresponds to a "nub" on the powerhead |
Explore related products
What You'll Learn
Mercury switch as a kill switch
A mercury switch is an electrical switch that can be used as a kill switch on a boat. When the boat tilts too much, the mercury inside the switch connects with metal electrodes, completing a circuit and grounding out the ignition, which kills the motor. This prevents accidental starting of the motor and also shuts the motor down if the boat pops out of the water, preventing over-revving and protecting the engine.
The most common type of mercury switch is the mercury tilt switch, which is in one state (open or closed) when tilted one direction with respect to horizontal, and the other state when tilted the other direction. This type of switch is usually mounted to the engine at a 45-degree angle, so that when the engine is tilted past this angle, the switch is activated and kills the engine.
Mercury switches can also be designed as displacement switches, which use a 'plunger' that dips into a pool of mercury, raising the level in the container to contact at least one electrode. This design is used in industrial applications that need to switch high current loads frequently.
Exploring Scaldis: Finding Your Dream Sailing Yacht
You may want to see also
Explore related products
Mercury switch as a safety feature
A mercury switch is a safety feature on a boat that prevents accidental starting of the motor. It is an electrical switch that opens and closes a circuit when a small amount of liquid metal mercury connects metal electrodes to close the circuit. When the boat tilts too much, the mercury makes a connection inside the switch, grounding out the ignition and killing the motor. This prevents the boat's engine from being damaged by over-revving.
The switch is designed to be mounted to the engine at a 45-degree angle. When the engine is tilted beyond this angle, the switch makes a connection and shuts down the engine. This can also happen if the motor pops out of the water while running.
There are several different basic designs of mercury switches (tilt, displacement, radial, etc.), but they all share the common design strength of non-eroding switch contacts. The most common type is the mercury tilt switch, which is in one state (open or closed) when tilted in one direction and the other state when tilted in the other direction.
It is important to ensure that the mercury switch is installed in the correct orientation. If the switch is installed in an "already too tilted" position, it may shut down the engine even when the boat is not tilted beyond a safe angle. To check the orientation, there should be a "slot" or hole on the body of the switch that corresponds to a "nub" on the powerhead. If the orientation looks correct, the switch can be tested with an ohmmeter; it should have no continuity when "upright", then get continuity when it is rotated 60-90 degrees or so.
Understanding Boat Speedometers: How Do They Work?
You may want to see also
Explore related products
Mercury switch design
A mercury switch is an electrical switch that opens and closes a circuit. It does this when a small amount of the liquid metal mercury connects metal electrodes to close the circuit. There are several different basic designs, including tilt, displacement, and radial, but they all share the common design strength of non-eroding switch contacts. The most common is the mercury tilt switch. This is in one state (open or closed) when tilted one direction with respect to horizontal, and the other state when tilted the other direction.
The mercury displacement switch uses a 'plunger' that dips into a pool of mercury, raising the level in the container to contact at least one electrode. This design is used in relays in industrial applications that need to switch high current loads frequently.
On a boat, a mercury switch serves two purposes. Firstly, it helps prevent accidental starting of the motor when it is in the upright position. Secondly, if the motor pops out of the water while running, it shuts the motor down, preventing over-revving and protecting the engine. It is usually mounted to the engine at a 45-degree angle so that when the engine is tilted up that far, the switch makes a connection and kills the engine.
Cars That Double as Boats: Transforming Vehicles
You may want to see also
Explore related products
Mercury switch installation
A mercury switch is an electrical switch that opens and closes a circuit when a small amount of liquid metal mercury connects metal electrodes to close the circuit. The most common type is the mercury tilt switch, which is in one state (open or closed) when tilted one direction with respect to horizontal, and the other state when tilted the other direction.
To install a mercury switch, you will need to mount it to the engine at a 45-degree angle. This means that when the engine is tilted up to that angle, the switch will make a connection and kill the engine. There should be a "slot" or hole on the body of the switch that corresponds to a "nub" on the powerhead to make sure that the switch is in the proper orientation. If that looks right, then take the switch off and test it with an ohmmeter; it should have no continuity when "upright", then get continuity when it is rotated maybe 60-90 degrees or so.
Boat Launching Sign: What Color is Correct?
You may want to see also
Explore related products
Testing a mercury switch
A mercury switch is an electrical switch that opens and closes a circuit when a small amount of the liquid metal mercury connects metal electrodes to close the circuit. The most common type is the mercury tilt switch, which is in one state (open or closed) when tilted one direction with respect to horizontal, and the other state when tilted the other direction.
To test a mercury switch, first check the orientation of the switch. There should be a "slot" or hole on the body of the switch that corresponds to a "nub" on the powerhead to make sure that the switch is in the proper orientation. If this looks correct, then take the switch off and test it with an ohmmeter. The ohmmeter should show no continuity when the switch is upright, and then get continuity when it is rotated 60-90 degrees or so.
If the switch is not functioning correctly, it may be installed in the wrong orientation, or it may be bad and making contact all the time.
Customizing Your Boat: Adding Paint in World of Warships
You may want to see also
Frequently asked questions
A mercury switch is an electrical switch that opens and closes a circuit when a small amount of the liquid metal mercury connects metal electrodes to close the circuit.
The mercury switch is a kill switch. When it gets tilted too much, it makes a connection inside and grounds out the ignition, killing the motor.
The switch serves two purposes: one, it helps prevent accidental starting of the motor when it's in the upright position; two, if the motor pops out of the water while running, it shuts the motor down, preventing over-revving.
