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  #1   IP: 68.220.174.45
Old 08-07-2007, 09:56 PM
Gary Gover Gary Gover is offline
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Gasoline Vapor

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.
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  #2   IP: 38.118.52.41
Old 08-08-2007, 01:57 AM
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Gary,

A very professional approach. Thank you for sharing.

Don
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  #3   IP: 24.224.206.117
Old 03-20-2011, 10:00 PM
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Red face But for the grace.....

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.
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The pessimist complains about the wind.
The optimist expects it to change.
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Old 03-21-2011, 05:56 PM
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Al Schober Al Schober is offline
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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

Last edited by Al Schober; 03-21-2011 at 05:58 PM.
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Old 03-22-2011, 07:33 AM
ArtJ ArtJ is offline
 
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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.
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Old 10-08-2011, 03:21 PM
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Smile A bit of patience and avoid the Harp.

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.
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The pessimist complains about the wind.
The optimist expects it to change.
The realist adjusts the sails.
...Sir William Arthur Ward.
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  #7   IP: 24.152.131.220
Old 10-08-2011, 03:54 PM
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This happened to me

I don't recall if I posted this before but a few years ago I had this exact sphincter episode.

I was merrily walking down the dock to my boat when about 2 slips away I could detect the distinct smell of gasoline fumes. I thought poor sap, he's got a dangerous condition, hope he doesn't take out the rest of us in the process. By the time I stepped into my cockpit it was clear that I was the poor sap.

First thing I did was step off the boat and turn off the shore power at the dock breaker. Next was to open up the boat as much as possible and start looking for the culprit. I knew anything left on had to be switched off but not haphazardly, it had to be done so no spark was produced. The only things I leave on when I'm not at the boat are the bilge pump (controlled by a float switch) and refrigeration.

I reasoned that the bilge blower switch was located at the very stern of the boat and pretty high. Also the blower itself is mounted high and is supposed to be ignition proof. That seemed like the best thing to get going to evacuate the fumes so I said a little prayer and switched it on. OK, all good. I then turned off the battery switches except for the one feeding the blower. Those switches are supposed to be ignition proof too. That went well.

So, I'd done as much as I could do regarding minimizing an ignition source until I was comfortable the fumes had been exhausted.

Post sortie debriefing
The fuel level in a full tank on a Catalina 30 is a little higher than the carburetor and my float valve had a speck of debris allowing a slow siphon. I have a small catchment below the carb and that was full and overflowing into the bilge although not much reached the bilge. I sponged up the spillage and went after the residue with soap and water.

I admit I'd been too lazy to dig under the quarter berth to close the tank valve which was the real issue. Since that episode I've installed a Xintex MB-1-R fume detector that automatically operates the blower (it's left on when I'm not at the boat) but most importantly I've installed a manual fuel shutoff valve immediately ahead of the carburetor and accessible without opening or removing anything. It's now a routine part of shutting down the engine.
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prior boats 1987 Westsail 32, 1970 Catalina 22
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Last edited by ndutton; 11-05-2017 at 09:44 PM.
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Old 10-08-2011, 05:48 PM
hanleyclifford hanleyclifford is offline
 
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Good narrative, Neil and we might add that the Coast Guard requires all "inspected vessels", gasoline or diesel, to have a fuel shut off easily accessible to the operater. A needle and seat is the worst possible "shut off" valve.
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Old 10-08-2011, 07:24 PM
weephee weephee is offline
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Gasoline Vapour

Can you give an example of a good fuel shut off valve. I would like to have one on the outlet of my Racor filter. There is one on Ebay, but I really don't want to spend $45 for it. Thanks
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  #10   IP: 24.152.131.220
Old 10-08-2011, 08:28 PM
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Here's one, 16 bucks plus shipping.

And this is the one I used with an extra port for my fuel purging and polishing system. It also serves as my shutoff valve.

Here are a couple of pics of mine. It's a little hard to see but note the price in the first pic, 6 bucks. Minney's is the greatest.

Name:  Fuel Diverter Valve.jpg
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Size:  106.3 KB Name:  Fuel Diverter Nameplate.jpg
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1977 Catalina 30
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prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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  #11   IP: 174.65.44.114
Old 10-08-2011, 11:35 PM
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Geez! You guys are scaring me!

If I install a shutoff valve before the Racor, just after the fuel tank, will this prevent a faulty float from emptying the Racor? I have a shutoff just before the mechanical fuel pump but access isn't what I would call great. I mean, I have to lift up the top stair and reach past the hot manifold to shut it down.
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  #12   IP: 24.152.131.220
Old 10-09-2011, 12:05 AM
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Technically yes, with a valve ahead of the Racor filter it won't empty through a faulty float valve but only because the system is closed or unvented. I'd guess you'd spill some fuel until a sufficient vacuum is created in the Racor to prevent fuel from flowing.

Y'know, with a valve like mine that has a mounting flange you can mount it just about anywhere and plumb a little fuel hose to and from. Mine is about a foot to port of the flywheel and the shaft goes through a bulkhead. A little trick I used was the nameplate is mounted with double backed tape and mounts over the countersunk screw heads that mount the valve. If you don't need or want the extra port you can block it off with a brass pipe plug.
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prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others

Last edited by ndutton; 10-10-2011 at 11:49 AM.
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Old 10-09-2011, 12:10 AM
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I'm thinking about getting one of those and mounting inside the port sail locker for easy access, since most everything I need to close up shop is in that locker anyway. I mean, mainsail cover and shore power cord etc. Thanks Neil.
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2/7/67 A4 Engine Block date
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Old 10-09-2011, 08:19 AM
weephee weephee is offline
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Gasoline Vapour

Thanks Neil. That's the shut off valve I was looking for only the ebay one I saw was $41.
http://cgi.ebay.com/ebaymotors/?cmd=...K%3AMEWAX%3AIT

Thanks again.
Larry
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Old 10-09-2011, 11:33 AM
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Yeah, eBay isn't what it used to be. The deals are more scarce these days and I'd say the auction you referenced is no deal at all.

I've brought this up before and probably shouldn't again except that I like mine so much. If adding a valve, getting the three port valve is a big step toward the automatic filter purging system I have. It requires some additional fuel hose, an electric pump and a little electrical but with it purging the air after changing the fuel filter is a dream (mine's a spin on cartridge type). I can also polish fuel through the filter returning it to the tank and drain the tank into jerry cans easily, all of which I've done.

Something to consider.
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1977 Catalina 30
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prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Old 10-09-2011, 12:55 PM
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Smile

I have one on the Prt side leaving the tank and one near the filter. Will attach a few pics later.
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"Odyssey"
1976 C&C 30 MKI

The pessimist complains about the wind.
The optimist expects it to change.
The realist adjusts the sails.
...Sir William Arthur Ward.
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Old 10-09-2011, 10:10 PM
Jlmatt Jlmatt is offline
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This is a quote from an article by Gordon Groene about the Atomic 4 published in 1976 in Motor Boating & Sailing. It was reprinted by Practical Sailor in May 1981.
"... Fuel should never be turned off to an engine-driven, diaphragm-type pump unless the shut-off valve is between the pump and the carburetor, because any interruption in flow on the suction side causes distortion of the diaphragm,--the major cause of diaphragm leakage"
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Old 10-09-2011, 11:09 PM
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Good advice.
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Old 10-09-2011, 11:37 PM
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does this advice apply to an electrical pump, or only mechanical pumps??
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Old 10-10-2011, 01:00 AM
hanleyclifford hanleyclifford is offline
 
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Quote:
Originally Posted by Jlmatt View Post
This is a quote from an article by Gordon Groene about the Atomic 4 published in 1976 in Motor Boating & Sailing. It was reprinted by Practical Sailor in May 1981.
"... Fuel should never be turned off to an engine-driven, diaphragm-type pump unless the shut-off valve is between the pump and the carburetor, because any interruption in flow on the suction side causes distortion of the diaphragm,--the major cause of diaphragm leakage"
This raises some intereting questions and issues. It would seems that Mr. Groene is concerned about running a diaphragm pump dry and distorting the diaphragm. Point taken, but consider this: if the fuel is shut off downstream of the pump and hence the pump left charged with fuel and open to the tank, what is the risk if the diaphragm has a leak?Now the potential exists to empty a fuel tank into the crankcase! IMO the solution is to shut off the fuel upstream of the pump, but do not run the carb dry as a routine procedure at shutdown.

.
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Old 10-10-2011, 01:40 AM
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I guess the real question is, how long are you shutting the system down for? If it's only short term, I think shut down just before the carb is good. If long term, I don't know. Maybe at the tank outlet? Might have to prime the system and check your lines for integrity if that's the case.
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Old 10-10-2011, 08:49 AM
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My P30 has an electric shut-off (solenoid valve) right on the tank, upstream of the mechanical pump. When the ignition is off, the valve is closed. I'm pretty sure it's original factory equipment. There is also a manual valve in between the tank and the filter (still upstream of the pump).
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Old 10-10-2011, 09:06 AM
smosher smosher is offline
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I have a P30 and I have a manual petcock, before the filter

Steve
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Old 10-10-2011, 11:50 AM
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Quote:
Originally Posted by ndutton View Post
...The fuel level in a full tank on a Catalina 30 is a little higher than the carburetor and my float valve had a speck of debris allowing a slow siphon. ...

In my Pearson 323, most of the volume of the fuel tank is above the level of the carb. The boat came with a Fuel/Trol electric cutoff valve mounted at the tank. It is wired to the ignition circuit, so as soon as I turn it off, the fuel supply is cut off. This seems like a pretty good solution, as I don't need to remember to do anything extra when securing the boat.
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