NGK TR5 SPARK PLUG

Function and technical context

The NGK TR5 spark plug is part of the ignition system of OMC Cobra outboard engines, being the component responsible for generating the electric spark that initiates combustion in each cylinder. It works directly in the combustion chamber, subjected to continuous cycles of high temperature and pressure, both in conventional carburetor configurations and in engines equipped with electronic fuel injection (EFI). Its iridium or resistive core, according to NGK's TR5 specification, guarantees a stable, high-energy spark that ensures complete combustion of the fuel, reducing consumption and unwanted emissions. If the spark plug loses efficiency due to wear or deposits, the engine may experience misfires, loss of power and difficulty starting, problems that can be especially critical in navigation.

When to replace this part?

The most common symptoms of a damaged spark plug in these engines include jerking or jerking during acceleration, unstable idling, difficulty starting when cold and a visible increase in fuel consumption; In advanced cases, black smoke may appear from the exhaust indicative of an unburned mixture. For heavy-duty marine engines, it is recommended to replace the spark plugs every season or every 100 hours of operation, which coincides with the general inspection of the ignition system. Changing the spark plugs preventively, without waiting for obvious faults to appear, is the most common practice among professional naval mechanics to avoid breakdowns at sea.

Equivalent manufacturer part numbers