Keeping in mind Twoowls comments above, the recommended spark plugs are RJ12C Champions (hot) or J8C (cooler) and Autolite 437 (hottest).
I want to try the Autolite plugs as I find that the Champions foul up pretty quickly.
09-27-2009 06:13 PM
The old manuals say 0.035", but the Moyer Marine archives have some postings talking about 0.030" for some plugs.
Atomic 4 Parts Catalogue and Operator Manual westerbeke, marine generators, engines, Official Siteor to to the Westerbeke main page and find Atomic 4 in the drop down list of products.
The Moyer Marine forum archives are full of useful info about plugs and everything else A4.
09-25-2009 10:10 PM
Points at 25 thousandths
Plugs at 30 thousandths
07-31-2008 09:52 PM
It is not as simple as it seems. It depends on the spark plug, the intensity of the coil and the compression of the engine. Larger gaps produce more power but require more coil for a hotter spark. Higher compression requires more spark power (coil) and high RPM engines usually use less gap. However since the Atomic 4 is around 9.3 compression, and best power RMM is around 2400, the gap can be quite large if the coil is reasonable. In auto racing we use a very large coil, relatively small gaps and really good plugs that rarely foul. Using the same heat range plug with platinum tips and thin wires we have very little fouling. I am sure the Atomic 4 would do well with this type of plug.