Spark plug
 

When should I replace a spark plug? Thinking about preventative maintenance on my 147 before winter. The current one is about 4 years old and still works fine. How to know/when to replace?

Thanks

When it's no longer working fine. If it's working, don't mess with it.

mines been in the engine as long as ive owned it and it still starts and runs fine, im planning to do a new plug and wire in the next few weeks just to make sure its top notch for winter.

I have developed a foolproof method of identifying bad spark plugs. You will need a multimeter for this. Measure resistance from the terminal stud to the threads where it screw into the block. If resistance is infinite, you got a bad spark plug. I have identified dozens of bad spark plugs this way .:Detective1:

How many good ones do you find?:biggrin2:

None, it works every time. They don't make them like they used to :biggrin2:

:ROTF1: :beerchug: