Re: [omc-boats] Last run of the season

On Fri, 1 Dec 2006, Andy Perakes wrote:
> That's an interesting failure mode experience, Ethan. I used to have a
> poster that showed various spark plug failures and reasons, but darned if I
> know what happened to it. I did find a nice link at Champion (see below),
> but there's nothing that looks related to what you experienced. (Some of
> the other brands might have more; I only checked Champion.) You are
> probably right that it had some minor damage early on and the stress cracks
> built up over time until it finally popped. You're especially lucky nothing
> fell into the cylinder and tore it up.

I've looked at them many times at auto parts stores and they're in the
back of several of my service manuals, but I definitely haven't seen this
failure mode.

Even searching google doesn't turn up many discussions of blowing out the
center of plugs. Most of the articles you find when search for "spark plug
blown out" discuss problems with Ford Triton engines blowing out entire
plugs due to inadequate thread depth (which requires replacing the head)
and older Peugeots, which also seemed to be prone to doing this (they're
typically repaired with thread inserts).

One other possibility I hadn't considered is that the plug could've stopped
sparking, causing the cylinder to fill with fuel and hydrolock would've
blown out the plug. That seems less likely though because of the signs of
gradual cracking.

I'm really hoping nothing was damaged, but I won't really know until I look
inside. Fortunately the outer electrode came out with the threaded part of
the plug, so all that could be left inside is the ceramic, the center
electrode, and the copper core. The only bit that is hard is the center
electrode, and that's pretty tiny. I'm going to ask around about borrowing
an endoscope this weekend. I might actually try pulling the head in the
spring, as a friend suggests that it is trivially easy.

> Are you using dry suits to wakeboard in 40F water? If so, how well do they
> work? I've tried skiing and sailing (wet sailing) in wet suits, but found
> the dry/wet/dry/wet cycles rendered them less effective (vs. just staying
> wet) as I was constantly needing to warm fresh water each cycle. I've never
> been able to try a dry suit and haven't been willing to put out the pile of
> cash they cost for fear they won't work much better or will be too much
> hassle to put on. Would be interested to hear your experiences with them,
> if you have any. Regardless, I give you much credit for braving that kind
> of weather!

Unfortunately we don't have water-skiing drysuits, so we're just going in
wetsuits. I have a suit which actually seals somewhat well on the ankles,
so if I get into the water carefully and keep my arms and head above water,
I only get wet up to my knees or thighs. It's still bone-chilling cold,
but once you get up it's ok - air temperature is what really matters then.
That's good for the first run, but once you wipe out, you're soaked
everywhere and really cold. Once your skin and the suit is wet, you're
cold even when you're up, and, like you say, they drain when you're up and
fill again when you wipe out. We were really only planning on doing a
couple runs per person and then heading back in. I know people who use
drysuits and they'll spend all day in cold water, but I've unfortunately
never been able to waterski with one myself! I love my drysuit for diving
though - I use it 7-9 months out of the year!

Ethan

-- 
<A HREF="http://www.engr.wisc.edu/~brodskye/"> Ethan Brodsky </A>
UW FutureCar Team Paradigm: Two-Year FutureCar Challenge Winner
UW-Madison Clean Snowmobile Team: Winner of the 2004 SAE CSC
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