Gasoline Vapor

[Gary Gover]

My greatest engine safety concern is for the possible accumulation of explosive vapor in the bilge. If I remember right, an ounce of gasoline properly mixed with air has the explosive power of a quarter pound of TNT.

The Atomic 4, being a marine engine, has features to manage the risk, such as are built into the carburetor and fuel pump, and I've taken some some additional measures. I've installed extra 'natural' ventilation for the bilge. I use an electronic gasoline vapor detector in the engine space. I run the bilge blower all the time the engine is running. I always run the bilge blower for five minutes before starting the engine and run it for ten minutes before starting after fueling. I close the boat up tight during fueling. I keep the bilge fairly dry to keep the vent ducting open and free of water.

Specially, because crankcase vapors contain unburned fuel and because the crankcase of the Atomic 4 is not sealed at the forward end of the crankshaft and because the engine's means of crankcase scavenging thru the carburetor flame arrester is so weak, I have ducted the crankcase vent pipe overboard and fitted that duct with an exhaust blower.

I annually carefully inspect using a checklist the fuel tank and all its lines and fittings to see that everything remains is good condition, tight and leak free. I have replaced any nylon fuel fittings with bronze fittings and any old flexible fuel lines with modern approved fire resistant lines.

An explosion onboard is my top engine safety concern, followed closely by similarly rooted risks of fire involving fuel or oil or risks of accumulation of engine vapors inboard.