The Universal Atomic 4 
The Universal Atomic 4 Most Yankee 30s came equipped with an Atomic 4 gasoline engine
for auxiliary power, as did thousands of other sailboats.
There were approximately 40,000 of these engines built up until
1985, when production ceased. As of 1998 about half of them were
still in use. The Atomic 4 is a safe, simple, and reliable engine
that will last indefinitely (or until the raw sea water
coolant rusts out the block) if routine maintenance is performed. Replacement parts are readily available
for routine maintenance and major overhaul. These engines are relatively
simple and can be maintained by an owner, particularly given the
support of the members of the Atomic 4 mailing list at Sail Jazz. Because
gasoline is highly flammable and explosive, maintenance and regular inspection
of the fuel tank, fuel tank hold-down straps, fuel line, fuel filter, fuel
pump, and carburetor, is critical. You don't want fuel leaks
or fumes on your boat. Despite the greater popularity of diesel auxiliaries
in today's newer boats the Atomic 4 has several advantages over diesel
engines: it doesn't stink, it doesn't vibrate, it's quieter, and
it starts reliably. If your engine has been neglected and you experience
overheating problems check the links below on flushing the engine and fixing
the thermostat housing.
Resources
Parts
Repowering
Overheating