My Atomic 4 has been a pretty reliable engine. During the great "No Start Debacle" of Summer 06, it became increasingly apparent that the problem had more to do with me than the engine. Something about putting spark plug wires on in the correct order, who would have known archaic tidbits like that?
Anyway, during the Great Solo Adventure of 06, I motored out of the marina rather than sailed. As always beforehand, I ran the blower. The surveyor when I bought the boat gave me an interesting trick to smell the exhaust vent when you first start the blower to see if there is any fume buildup. He mentioned then that he had never heard of a boat exploding because of an A4, but that the blower is a really good idea just in case. Now, I've actually had boat brokers tell me that it isn't worth even looking at a boat with an A4 because "they blow up". That self-serving statement aside, there is a widely held belief that gas engines will eventually blow up your boat.
So, I've done some research thanks the The Miracle that is The Google (TMtiTG). Not one mention, in fact the first result from "Atomic 4" explosion has this quote "One fact that I heard a few weeks ago is there has never been a gas explosion for an Atomic 4". It takes until the 4th page to find a result that actually mentions an explosion rather than the risk of or avoidance of explosions. And then, when you read that result, they're talking about propane explosions, not Atomic 4 explosions.
So, I'll continue to run the blower, put the spark plug wires on in order (1 2 4 3), and enjoy my trusty A4.