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Mercruiser 5.0 MPi 260Hp Spark Plug Gap!

  • #1
    Registered Users Posts: 7 ✭✭✭

    Hello everbody!

    Long time since i posted.. here it goes

    I have a 2009 Motor in my boat.

    As the title says its a Mercruiser 5.0 260Hp MPi with an alpha one version 2 leg.

    Im trying to find the right spark plug and spark plug gap!

    From the NGK spark plug finder link below they say use an iridium ITR5F13 with a gap of 1.5 mm

    From the Mercruiser parts finder using my motors serial number its saying use IRR4A15 but it doesnt mention a gap anywhere?

    Ive read, i think most of the forums and one guy is saying the 15 at the end of the part number means pre-gapped to 1.5mm ?

    Anyone crossed this bridge before and get a definite answer... i dont want to melt my motor out at sea!

    Is the NGK ITR4a15 plug already pre gapped? 0 votes

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  • It can be different depending on who built the engine and what parts they use, the gap for yours should be on a sticker on the flame arrester cover.


  • Thanks Fergal.

    The plug and gap is indeed listed on the side of the flame arrester but thats for the plug mercruiser recommenced in 2009. they have changed that recommenced plug a few times since then as per the mercruiser parts catalog.

    So in the end, I used 8 IRR4A15 leaving the gap as it was supplied. The boat is running very well. Hope this helps fellow googlers :-)

  • They may have changed with different fuel systems, disturbers, electronic ignition and so on over the years.
    Happy boating.