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.

[Don Moyer]

Gary,

A very professional approach. Thank you for sharing.

Don

[Mo]

Summer 2007 -

I was overhauling my boat when I first bought her...had built a trailer / cradle and had her in the driveway in front of my garage...walk in the park. Just finished the overhaul on painting, wiring etc etc etc. I was leaving the engine until last.

I had messed with the engine a bit and left the fuel shut-off open. Went in the house overnight and came out at 8am to go back at it. The sun was already beating on the deck.

It was only a miracle that I didn't have a cigarette in my mouth as I opened the hatch. The fumes hit me in the face. She had dumped at least five gallons of gas in the bilge..it ran through a malfunctioning carb that I had not even touched yet. I've been to a few of war zones but that was the closest I came to being blown up...the fumes were so strong that it just would have been a bang.

Carefully soaked it up with a car-wash sponge...squeeze by squeeze...into funnel and gas can. There are 2 fuel shut-offs on the boat. I ensure one is closed when I leave daily. I got that lesson without paying the price.

[Al Schober]

One of the first 'adds' to our A4 equipped boat was a fume sniffer. That was back in '88. Since then it's gone off twice, and neither time was related to the engine.
First was a gas jug for the dingy that had gotten onto its side in the lazarette. A slow drip was enough to trigger the sniffer.
Second time was while taking on fuel. Turned out to be a bad hose between the tank and the deck fill.
The first one makes me wonder about the folks that feel so safe because they have a diesel inboard - no need to worry about gas, right? Where do they store their gas jugs for their dingy? Or perhaps they have diesel outboards...

Al

[ArtJ]

We have to be careful with the gasoline fume detector mounting.
I had one become loose and fall into bilge water. It caused a alarm and
a expensive sensor replacement I think it was well over 100 bucks.

[Mo]

Hi Guys.

Not so common sense.

If you enter a boat and even have a hit of gas smell DO NOT TOUCH POWER SWITCHES....DO NOT TURN POWER ON...LEAVE OFF....open forward hatch, lazarettes, if your steps cover engine compartment remove them to let air flow through, lift out bilge flooring, and leave companionway open....Do not even touch the blower switch for 10 minutes .

If you don't have a detector, leave the boat area and come back 15 minutes later. Your nose gets accustomed to the gas smell and may deceive you. Leave for a period of time. Upon return, if you don't smell gas you MIGHT be OK to turn on the blower.

...then go TROUBLESHOOT the source.