Mercruiser MPI spark plug change frequency

[QBhoy]

Guys,
After the thoughts of the forum....
How often do we change the iridium and bloody expensive plugs on the above ?
Local Merc dealer reckons only when they noticing need it and not every year...
Thoughts...?

 

[Bondo]

Ayuh,... Wouldn't hurt to look at 'em every 500 hours or so,....

 

[QBhoy]

Hey Bondo....a privilege to hear a response from you...
I tend to agree.
The boat is a 2003, but only covered 350 hours. 200 of which, I have had the pleasure of putting on her in the last 2 seasons.
I changed them this spring and I'm pretty sure they are the original. Seemed to make a difference to performance and even the sound of her. Just that little bit sweeter running.
Noticed a slight speed increase, although this could also be the result of a clean and waxed bum !
Went with the AC Delco....is there a better equivalent NGK that you might recommend?

 

[Bondo]

Ayuh,.... I've run plain ole AC Delco MR43T plugs 500 hours, 'n the corners were just barely burnin' off,...

So long as the corners are sharp, it's still a Good plug,... the point on yer's,...

I worry more 'bout other brands rustin' into the head, 'n breakin' off,...

The MR's are an alloy body,...

 

[QBhoy]

Thanks Bondo.
They seem a bit delicate these iridium AC Delco plugs ...in comparison to the old ngk BR6FS I used to know and trust for the old 4.3 carbs.