Spark plug gap shrinking?

[tmmfont]

My motor is a 2009 250 Pro XS serial number 1B751847. I do my own maintenance every year and every time I change the plugs, I always check the gap of the old ones. When the plugs were installed, I had gapped them to .042-.044 using a wire gap tool. Once pulled, almost all the plugs are now at .036-.040. Motor never runs bad but maybe lost a little top end. This has happened with plugs bought from Mercury marine dealer and with plugs bought from Auto Parts store. Plugs are installed using a torque wrench and are not beat up on the ends. They actually look like they are burning properly; light/medium brown on the ends. Just curious if this is normal.

[bassburch]

I don't know if it's normal but I think I've had that happen too. Can heat or wear change the gap considerably like this? Does the metal arm retain some sort of memory or something?

[Savage]

It happens, nothing you can do, but re-gap.

[rocketman6965]

Thanks for the observation. That is why pro active maintenance is the best policy

[tmmfont]

Thanks for the replies. I’ve heard of the gap growing but not much information on shrinking. Thanks again. Guess that’s another good reason to change plugs once a year!