Check Your Plugs

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This topic contains 7 replies, has 3 voices, and was last updated by Mumbles Mumbles 2 weeks, 5 days ago.

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  • Mumbles
    Mumbles
    Canada Member - 2 Years
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    #178029

    A friend brought his recently purchased 1980 9.9 Evinrude over today for some much needed maintenance. It ran and started OK but when I pulled the plugs to do a compression test, here’s what I found on the plugs. The electrodes were badly worn and the gaps were near 0.050″ on both of them. They might be the original plugs as they are QL77J4’s and I haven’t seen those for ages. A set of good used QL77JC4’s got it running a lot smoother but I’ll pick up some NGK’s for it tomorrow.

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    outbdnut2
    US Member - 1 Year
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    #178076

    I saw that wear issue years ago on a 1965 V4 60 HP Johnson. Really old plugs on a heavily used motor. The gap got so wide that the spark found a shorter path to ground across the rotor, establishing carbon tracks on it, necessitating rotor replacement. Kind of like carbon tracking inside distributor caps on cars from the 1950s and 1960s.
    Dave

    Mumbles
    Mumbles
    Canada Member - 2 Years
    Replies: 4104
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    #178077

    The owner just picked his motor up and it’s running great except it’s running cold and should have the t-stat replaced sometime. It’s in pretty good shape generally and someone had replaced the water pump recently but I don’t know why they ignored the plugs.

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    fleetwin
    US Member - 2 Years
    Replies: 2659
    Topics: 32
    #178086

    Maybe someone yanked the thermostat out masking a grommet issue…Those plugs look like they have seen a lot of high speed use….

    Mumbles
    Mumbles
    Canada Member - 2 Years
    Replies: 4104
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    #178092

    Could be but I don’t think the powerhead has ever been touched. The clamps holding the wiring in place don’t show any sign of ever having been straightened out and the paint on the bolts holding the water cover on isn’t chipped too badly. Just some signs of normal wear and tear from some salt water use. She’s a virgin! The owner will be bringing it back later in the summer to get the t-stat done so I guess we’ll find out for sure then. I suspect it’s stuck in the open position.

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    fleetwin
    US Member - 2 Years
    Replies: 2659
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    #178098

    You are right, that cover has never been touched…Never been badly overheated either…The owner should spend some dough to take care of that nice engine, can’t replace them for sure….

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    fleetwin
    US Member - 2 Years
    Replies: 2659
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    #178099

    If this is a salt water engine, it is worth spending the cash to do the grommet, before overheat sets in….Maybe the powerhead has already been off to do the grommet, seems unlikely though, you will know when you look at it again….1980 was the second year for the bad grommet set up…

    Mumbles
    Mumbles
    Canada Member - 2 Years
    Replies: 4104
    Topics: 420
    #178114

    I’m pretty sure it was mostly used in fresh as I didn’t find any real corrosion issues on it. The gearcase and pump bolts came undone quite easily and everything had been greased. It had been taken care of.

    I’m sure the grommet is OK and it’s the T-stat which needs attention as it flows water well out of the telltale and it also starts pumping like a garden hose out of the idle relief in 10-15 seconds once everything inside is filled up. All of my other 9.9’s take close to a minute for the stat to warm up and open before any water comes out the idle relief ports. When the owner was here yesterday, it wouldn’t get any warmer than 78 F while running in gear at a fast idle. It’s running too cold.

    I gave him a list of the parts needed to remove the powerhead to get at that grommet so if he picks them all up, I’ll do the grommet to while it’s in. It will give him peace of mind knowing all is well.

    • This reply was modified 2 weeks, 5 days ago by Mumbles Mumbles.
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