NGK TR55 SPARK PLUG

Function and technical context

Ignition in a marine petrol engine depends on the spark occurring at the exact moment and with sufficient energy to ignite the air-fuel mixture in each cycle. The NGK TR55 spark plug acts within the ignition system by generating that electrical discharge between its electrodes, initiating the combustion that drives the piston and, ultimately, the propeller. Its reinforced ceramic insulator and precision electrode design are essential to maintain the stability of the spark against humidity, environmental salinity and sudden temperature changes typical of the marine environment. A failure in this component is not limited to difficult starting: it can lead to intermittent misfires, increased fuel consumption and deposits in the combustion chamber that compromise the useful life of the engine.

When to replace this part?

The most common symptoms of a worn or bad spark plug in a marine engine are: slow or repeated starting, rough idling, jerking or loss of response during acceleration, and a visible increase in petrol consumption. As a general rule, spark plugs in marine petrol engines should be inspected during each seasonal maintenance and replaced at least every 100 hours of navigation, since the saline environment accelerates the corrosion of the electrode and the deterioration of the insulation much faster than in land applications. Preventatively replacing spark plugs before they cause failure on the open sea is the most economical decision any boat owner can make.

Equivalent manufacturer part numbers