YAMAHA IGNITION COIL 670-85640-00

Function and technical context

The ignition coil is the essential component of the ignition system that transforms low voltage current into high voltage to generate the spark at the engine spark plugs. In Yamaha F4 outboard engines, this coil works in coordination with the ignition circuit to ensure precise combustion of the air-fuel mixture in each cylinder. Proper operation is critical to maintaining engine power, efficient fuel consumption and reliable starting, especially in demanding boating conditions or in salt water where corrosion accelerates the deterioration of electrical components.

When to replace this part?

Typical symptoms of a faulty ignition coil include difficulty starting, loss of power under load, misfires that are intensified by humidity, and in advanced cases, inability to start the engine. Ignition coils do not have a fixed maintenance interval, but their condition should be checked at each seasonal inspection, especially after long periods of non-use or on boats exposed to saline environments. Preventively replacing the coil when it shows signs of weakening avoids being left without propulsion in the water and prolongs the useful life of the rest of the ignition system.

Equivalent manufacturer part numbers