Sudden Spark Plug failure

[jkenan]

Went out Saturday out of Beaufort, NC in 20-25k, and sailed to Cape Lookout to Anchor. Engine would not start when it came time to Anchor, so we did it all under sail. After troubleshooting the engine, it boiled down to the spark plugs not sparking (all of them). Replaced them with a new set I had on board, and everything worked fine.

We motored down the ICW the day before and engine ran great, as it also did that morning getting out of the inlet. It was rough that day, and we rode the sleigh all the way to the cape on a beam reach with a slight following sea.

What would cause all four plugs to foul at once?

Also, the next morning it was hard-starting, but finally did. It was also about 38 degrees outside. Do A4's have difficulty starting when it's cold? Motored about 8 hours that day with no other incident, and it restarted fine after refueling in Oriental, NC.

[tenders]

A slipped choke cable could cause the engine to run rich and all four plugs to foul.

My A4 has ALWAYS been hard to start after November 1.

[David Masury]

What may have actually happened... while motor sailing, you may not have been moving along close to hull speed and lugging the engine down, especially if you are going a distance, will foul the plugs....I changed my plugs from Champions to Autolite 437's....a better plug and much less prone to fouling and I have had no problems with fouled plugs.

David

[Don Moyer]

John,

The condition of spark plugs is a reflection of almost every other aspect of the engine's general health. It's therefore difficult to always pinpoint the exact cause of an anomalous plug indication. If we start with the assumption that an engine with reasonable compression (85 psi or more), a good fuel mixture (a gallon an hour or less at normal cruise), oil consumption less than a quart in 50 hours, an operating temperature 140 degrees or higher, strong ignition and properly timed (3/8" to 1/2" secondary discharge between coil lead and the head, and running at a reasonable cruising RPM (1800 to 2000 RPM) should not experience fouled plugs, then these items would make a reasonable check list of things to check when plugs foul quickly.

Don