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Single-point drain helps boaters shed water quicker
A simple pneumatic circuit requires no external power source
By Kevin Russelburg, Contributing Editor -- Design News, March 12, 2001
Stillwater, OK —While boat engines depend on cooling water drawn from the lake, river, or ocean during operation, the water must be drained in order to prevent freeze damage during the winter months. With conventional engine drainage systems—some having up to six plugs that need to be removed—the process can be cumbersome and time-consuming.
The Single Point Drain System from MerCruiser allows boaters to reliably drain the seawater from their engines in a mere five minutes. "This system provides an extremely convenient and user friendly means of draining seawater," says Matt Jaeger, an engineering specialist at Mercury MerCruiser.
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| The Single Point Drain System from MerCruiser allows boaters to reliably drain the seawater from their engines in a mere five minutes. |
The system is a pneumatic circuit consisting of two normally closed actuators. One actuator is located on each side of the 8.1L V8 engine. When the air circuit is pressurized, a drain orifice on each side opens. The seawater that is trapped in the engine and other components then drains through these openings and into the bilge of the boat.
The actuators in the Single Point Drain System are air cylinders, integrated with seawater handling components. The valve (cylinder rod) in each actuator is extended by spring force when the actuator is closed. In this case, the valve stem intersects the water passage in the actuator housing. The high velocity of the waterflow(>/=3 m/sec at wide open throttle) in the passage during engine operation keeps the area of the valve stem and housing intersection clean and free of debris.
"We selected pneumatics over mechanical, electrical, or hydraulics, because it offers several advantages. No external power source is required, it is environmentally friendly, and any air source may be used," says Jaeger.
To ensure proper function, two pressure indicators (one per actuator) provide feedback to the operator. The indicators tell the operator that the actuators are open and that water should be draining.
To ensure that the system will be reliable for the seven to ten year expected life of the engine, all components are made of corrosion-resistant materials. Both actuator housings are UNS C87500 Silicon Brass. Machined UNS C48500 Leaded Naval Brass is used for the valve stem in the larger actuator, and the valve in the smaller actuator is PET thermoplastic. Most of the other components are a combination of UNS C36000 Free Machining Brass and either PBT or Acetal thermoplastic. Each seal that contacts seawater is made from an ethylene propylene material.
Because system failure is always a concern with designs that rely on a single point of operation, engineers incorporated a redundant drain system. Three T-Headed plugs can be removed and installed by hand if necessary.
Additional Details
Contact Matt Jaeger, Mercury MerCruiser, 3003 N. Perkins Rd., Stillwater, OK 74075; Tel: (405) 743-6739; E-mail: matt_jaeger@ mercmarine.com.
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