NGK BR7HS-10 SPARK PLUG

Function and technical context

The NGK BR7HS-10 spark plug operates at the core of the ignition system, acting as the element that transforms high-voltage electrical energy into the spark that initiates the combustion of the air-petrol mixture in the cylinder chamber. Its position in direct contact with combustion gases continuously exposes it to extreme cycles of temperature and pressure, in addition to humidity, salt and corrosive agents typical of the marine environment. The thermal degree of this reference - designed to evacuate heat in a controlled manner - is decisive to avoid both pre-ignition due to overheating of the electrode and fouling due to carbon in engines that work at low or partial speeds. A failure in this component interrupts or deteriorates the combustion sequence, which results in loss of power, increased consumption and, in extreme cases, piston knocking due to incomplete combustion or uncontrolled ignition.

When to replace this part?

In two-stroke outboard engines, the clearest signs of a bad spark plug are difficult cold starting, irregular idling with vibrations or "miss", loss of acceleration under load and increased mixture consumption. For this type of propellers, it is recommended to inspect the spark plug every 100 hours of use and replace it at the beginning of each nautical season, or sooner if the electrode shows erosion, the insulator appears blackened by carbon or cracked, or the air gap has changed from the manufacturer's specification. Replacing it preventively at each seasonal tune-up is the simplest and most economical intervention to guarantee safe starting and optimal performance of the propeller in any navigation situation.

Compatible engines

Mercury/MerCruiser