PSA for inboard gas owners.....

[Lou C]

Gas fumes are a significant hazard for gas inboard owners. In addition to sniffing before starting up, proper fueling practices and use of the blower, it's a good idea to have a gas vapor detector installed on your boat. I went one step further, I got a hand held combustible gas detector (detects gasoline, propane, etc) to check all around the gas tank, around the carb, fuel pump and fuel lines. I tested it with a gas can and a gas stove and this thing WORKS! Lucky I found no leaks in the boat, the alu tank is 38 years old!
Especially useful if you have done work on the fuel system recently like a new tank, fuel hoses, pump or carb rebuild.... remember fuel vapors are heavier than air, check way down at the bottom of the bilge.

 

[airshot]

Not only inboards, many outboards have built-in fuel tanks, so do not overlook the possibility of a leak there. With many enclosed below the floor or under a gunwale, trapped vapors can still be a major issue !

 

[Lou C]

Certainly true.
I think a good idea is for the fuel tank coffin so to speak to have vents on the front and rear bulkheads, that helps also with drying out any moisture.

 

[airshot]

Certainly true.
I think a good idea is for the fuel tank coffin so to speak to have vents on the front and rear bulkheads, that helps also with drying out any moisture.

Tell that to the mfgrs....

 

[Lou C]

When/If I have to replace the tank, I plan on adding them, and re-glassing the coffin.

 

[DeepCMark58A]

My master craft is a very well maintained 1990 have never had a problem, you can rig your blower so it is on when the key is on.

 

[Bugzilla46310]

Don’t disagree with any of this, but the engineer in me got me thinking if venting could cause a problem if there was a leak. If the active leak caused the vapor concentration to be outside the explosive range, you won’t go boom. From the internet:

The combustion concentration range for gasoline vapor is defined by its Lower Explosive Limit (LEL) of approximately 1.4% and an Upper Explosive Limit (UEL) of about 7.6% in air. This means that gasoline vapor can ignite and burn only when its concentration is between these two limits.

 

[Pmt133]

If there is a leak with how mine was designed, it runs directly into the doghouse... in my use case I don't know venting around the tank makes much a difference. The bulk head is better sealed after my rebuild than factory though.

 

[Lou C]

True but if the tank coffin is vented, & there is a leak in the tank (often at the bottom due to water not escaping) that vapor will become apparent sooner or later. You could still have a leak whether or not it's apparent.
Alternatively, I think if you have a hatch over the tank like my boat does it's a good idea to pull up that hatch at the start of each season and use sniffer to check all around the tank, fittings, hoses etc. Not a fan of designs with no hatch, only a pie plate cover, for accessing the tank. You can have a dangerous leak and not know it.

 

[Chris1956]

There is a large difference between inboard engine explosive fume risk and outboard engine explosive fume risk.

Inboard engines have the spark plugs, coils etc, in the shared bilge space. That is why the USCG created regulations in 1940 about enclosed engines in boats. That is why modern inboard engine boats have blowers.

Outboard engines have the spark isolated from the bilge, making them much safer. Blowers are not required on these, despite the use of built-in fuel tanks.

One other note: Natural gas is lighter than air, whereas gasoline fumes, and propane are heavier than air. Natural gas will dissipate into the atmosphere, where the others sink into the bilge where they can explode. Older boats used alcohol in their galleys. I will guess the alcohol fumes are lighter than air as well.

All boats should have marine-rated electronics, including battery switches, bilge pumps, PTT motors, etc. since they are spark-proof.

 

[airshot]

True but if the tank coffin is vented, & there is a leak in the tank (often at the bottom due to water not escaping) that vapor will become apparent sooner or later. You could still have a leak whether or not it's apparent.
Alternatively, I think if you have a hatch over the tank like my boat does it's a good idea to pull up that hatch at the start of each season and use sniffer to check all around the tank, fittings, hoses etc. Not a fan of designs with no hatch, only a pie plate cover, for accessing the tank. You can have a dangerous leak and not know it.

Exactly....this is the reason I do the smell testing often ! My boat is trailered and spends most of its time in my barn. Having no wind is nside, it should be easy to sniff any fumes. Before every trip, I climb in the boat, make sure everything is stowed, make everything is in its place, check batteries from the individual voltage testers on each battery and make sure there are no gas fumes. Only takes a couple minutes, well worth the time ! My built-in tank has some venting, not great, but their is some venting around the tank, and it is a good plastic tank. Every few years I open the floor to check/ replace the hoses connected to the tank, any sign of dry or cracking, they get replaced....

 

[IslandExplorer]

I really like the idea of the handheld one you were recommending Lou. I also take fuel vapors very very seriously and realize no matter how concentrated- the point where they meet air is definitely not going to be too concentrated to ignite. How much was that convenient handheld tester that you got? I might grab one of those for my safety kit myself.
Built in is nice but portable really would be better so you can spot check suspect areas like you said. Added benefit that you could hop in another boat thats having a problem with it and help em out.

 

[Lou C]

TOPTES PT 520A, $33.99 Amazon
tested it with an open gas can and gas stove, definitely alarmed!