Spark plug gap

[nennedk]

I was about to change my spark plug on my mercruiser 5.0L (2002) so I bought the recommended ngk’s but as seen on the picture there’s a visual gap difference. Should I go with the new ones as is or re gap them as the old ones? (By the way does the old ones look ok). Thanks

 

[Alumarine]

If those are the correct plugs the gap should be .045"
What does the sticker on the motor say for correct plugs and gap?
The serial number of the motor is more important than the supposed year of the motor.

 

[nennedk]

Didn't realize the sticker tells it It says AC-MR43LTS - 0.045. Engine serial is 0M359543. If i assume that the new ones is 0.045 (i will measure) and the existing ones has a too big gap, what should be the consequences?

 

[GA_Boater]

Anyone trusting pre-gapped plugs without verifying is asking for trouble. And eyeballing the gap against the old plug is useless because plug gap widens during use as the electrodes erode. Also who can say the old plugs were gapped correctly to start with?

Too wide a gag can cause misfiring depending on the condition of the rest of the ignition system.

 

[nennedk]

Okay i have now measured the new plugs and they all are .028 so I think the old ones which visually have a bigger gap is .045. Should I widen the new ones? And why are they all wrong?

 

[Maclin]

Plug gap is determined by the engine manufacturer based on ignition design, combustion chamber design and other factors. Any given spark plug may be specified for many different engine applications. The spark plug manufacturer has to choose a gap to set a gap for their process, and all spark plugs with a particular model designation get set the same way. Always check and reset the gap as needed before installing new plugs.

 

[Mercruisermike85]

It’s amazing the important information you can find on the flame arrestor, everyone told me .35 and the specs on my flame arrestor call for .45

 

[Maclin]

That's a BIG gap to be sure like missing a 0 after the dot big.

 

[garbageguy]

I like a fresh set of plugs too. Why are you changing yours? Your old ones look OK from those pics, a bit of carbon build-up. I'd be curious to see what others think about the condition of your old plugs.

There are some good websites on how to read spark plugs

 

[scoflaw]

Photo isn't the best, light tan is the color you want

 

[nennedk]

Thank you all. I have now regapped them all. I'll expect to try them next week. And the reason i'm changing them is only because i don't know how old they are, and that the new spark plugs came together with a service kit i bought last year, so they was just sitting there begging to be used

 

[Bondo]

I like a fresh set of plugs too. Why are you changing yours? Your old ones look OK from those pics, a bit of carbon build-up. I'd be curious to see what others think about the condition of your old plugs.

There are some good websites on how to read spark plugs

Ayuh,.... The take-outs are perfectly Fine,....
A little black, as the motor probably idled awhile before it was shut-down last,....
WOT colors are probably quite different,....

A worn spark plug will have the sharp corner edges, rounded over, both on the tip of the electrode, 'n the end/ edges of the ground strap,....

Boaters like to change spark plugs, 'n coils, because they Can,.......
99% of the throw-aways are perfect good parts,.....