"Marine" parts vs. cheaper ones

[BOFH]

There has been a lot of talk lately about "marine" carbs, distributers and ignitions. Everyone is questioning the laws and enforcement in a given spot... Since this is a major topic, I want to start a thread on it.
Law - Everywhere. It is a US Coast Guard thing, and all vessals must comply. Enforcement varries, but it is the law everywhere.
Difference - "Spark Protected" - Starters, Alternators, Points, and motors spark. It is how they work. "Spark Protected" or "Ignition Protected" means that any vents are sealed, vented outside the boat, or grounded. The last part can just be a screen, and is why K&N filters are spark arrestors.
Difference - Carbs - This is simple. All vents are to the inside of the carb. An FI system would have to have sealed electronics, and internal venting to ge legal, and safe.
Safety - Why am I doing this? Several years ago, I saw a boat blow up at a fuel dock. It was an outboard sport fisher. It turned out that the guy replaced his blower with a plane old squirel cage from the hardware store. He filled his tank, and some gas spilled, and ran down the deck. Like a good capitan, he hit his bilge fan before starting the external moter. This is all good safety, right up to the point where the non spark protected fan ignited the fuems below deck. It split the boat right allong the hull seam. The owner survived, but was blown about 30 feet up, and 20 feet forward. If anyone had been below, they would probably not have survived.
Everyone talks about how the engine compartment is open, but gas fumes sink. This is why the blower is in the bottom. Think about this when you are looking to save $100. Hell, thats not even a fill up these days. :-)

[Boatcop]

Good Topic.
To understand the need for marine shielded components you have to understand what is occuring in the engine compartment.
Gas fumes sink and collect in the bottom of the boat. Any spark and you have an explosion. It's a well known fact that the fumes from 1 cup of spilled gasoline equal the explosive force of 10 sticks of TNT.
Marine shielded alternators, generators, distributers, and starters have wire mesh around any openings. This allows proper ventilation/cooling of the component, while containing the spark inside the unit. When the fuel/air ratio reaches an explosive state, an explosion still occurs, but is contained harmlessly within the component. Without shielding the small explosion leaves the component and ignites the fumes in the rest of the engine compartment making the whole boat go BOOM!
Fuel pumps are a little different. Automotive fuel pumps have a weep hole, which lets the owner know when there is a diaphram failure. In a car, this is little more than an annoyance resulting in wasted gas and a stain on the driveway.
But in a boat, the fuel collects in the bilges and turns the boat into a potential bomb. FOr this reason, marine fuel pumps have a nipple where the hole would be, and a hose from the nipple to the carb intake. With this set-up, any leaked fuel is sucked back through the carb.
Backfire flame arrestors are the thngs that must be installed on the intake of all inboard gas powered boats. These are to prevent any backfire flames from igniting any gas fumes, material or people on the boat.
Carburators are not included in the list of required marine components, but hoses, wiring and fittings are.
Bilge blowers are kind of mis-labled. They don't "blow" fresh air into the bilge, but rather suck the fumes out. They should be marine type, installed in the bilge exhaust ducting, with the end of the duct (hose) in the lowest part of the bilge, but not so low to be submerged in any fluids that may be there.
I've investigated dozens of boat fires, and in nearly every case, one or more of the components were not marine shielded. If a marine mechanic installed or re-installed any of those components, then they would be liable for the explosion and resulting fire. If the owner installed the non-marine devices, their insurance would most likely deny coverage.
They may be a few dollars more. But what's a few hundred bucks on a $30,000+ boat.

[Liberator TJ1984]

Alan, I am taking that you do not have to run a marine style carb in an enclosed compartment..I thought you did ??

[RandyH]

Liberator TJ1984:
Alan, I am taking that you do not have to run a marine style carb in an enclosed compartment..I thought you did ??Good Question, I thought the J tubes and the seals where required in the Marine Carb. I hope you can clarify here Alan, Thanks in Advance.
Randy

[Boatcop]

I haven't seen "Marine Type" or "Coast Guard Approved" carburators, however there are standards which must be followed on carburators used in Marine Applications. Those standards from the Code of Federal Regulations are: (33 CFR)
Sec. 183.526 Carburetors.
(a) [Reserved]
(b) Each carburetor must not leak more than five cubic centimeters
of fuel in 30 seconds when:
(1) The float valve is open;
(2) The carburetor is at half throttle; and
(3) The engine is cranked without starting; or
(4) The fuel pump is delivering the maximum pressure specified by its manufacturer.
(c) Each updraft and horizontal draft carburetor must have a device that:
(1) Collects and holds fuel that flows out of the carburetor venturi section toward the air intake;
(2) Prevents collected fuel from being carried out of the carburetor assembly by the shock wave of a backfire or by reverse air flow; and
(3) Returns collected fuel to the engine induction system after the engine starts,
The question would be whether a standard automotive type carb would conform to these standards. When I ran the Spectras on the River for the Coast Guard in the late '70's, we had 800 CFM dbl pumper Holley's on our 454s. These were installed by Burbank Marine to COast Guard specifications and certified as meeting required standards.
What they are looking for is the inability for the carburator to introduce liquid fuel into the engine compartment through the throttle body.
If anyone's interested, the entire list of required motorboat equipment and their construction requirements is at:
CFR Title 33

[Hotcrusader76]

The only true "safety features" on a Marine carb that I have researched are three things:
1.J-tubes for fuel venting
2.Throttle shafts that won't leak outside the carb body
3. Anti-roll over squirters
Other than that, the fuel metering is a little richer on the bottom end, off-road style spring loaded needle and seats, and the certain Marine carbs are corrosion protected.
All of these features can be a no cost up-grade when overhauling an automotive Holley carburetor.
-Ty
[ August 14, 2002, 06:45 PM: Message edited by: Hotcrusader76 ]

[RandyH]

Thanks guys, this is great info.
randy

[Boatcop]

One last note on the enforcement of these standards.
The Coast Guard requires them on all new vessels sold in the US, and manufactured after the date each specific standard was adopted. The requirement is for manufacturers and dealers. Most (and I emphasize MOST) state laws don't address the standards in their state statutes, and even fewer require the owner to maintain those standards.
What this means is that in many areas, the owner can do anything they want to their boat's engine, (with the exception of back-fire flame protection). If Joe Back-Yard-Mechanic wants to replace that $300 Marine starter with a $19.95 Pep-Boys rebuild, no law prevents him from doing it, or running it. eek!
However, that fact will come out when the explosion and fire is investigated, and the insurance claim will be denied. (Notice I said "WHEN"?)
Keep that in mind when your motor-head brother-in-law says he can fix your boat a lot cheaper than the Merc dealer downtown can.

[79Hawaiian]

Great topic. I have been a bit (or a lot) ignorant on the topic. My boat does not even have a blower but I did have an experience when the front bowl was spraying gas on the manifold due to a failed gasket. I posted a previous topic asking about replacement distributor suggestions and was leaning towards an automotive product. Looking back to the time my manifold was saturated with gas I am thankful I had the shielded distributor! Screw the boat, I don't want to burn on of my good friends who are sitting in back. Boats can be replaced, god forbid I caused a friend or family member to be injured. That’s when the $100 really becomes insignificant.

[Rexone]

I wish we could get more people to realize the importance of these marine parts. We are constantly trying to educate people why to buy and use the more expensive marine fuel pumps, distributors, starters, alternators...the list goes on. It's amazing to me the number of people who just don't get it. I guess they've never seen or heard of gasoline exploding.
On the insurance aspect, I'm sure claims would be denied when it's discovered non approved marine parts have been used. I'm also guessing that anyone that knowingly installs a non-marine approved part, weather it be a mechanic or an individual doing his own work, that ends up causing an explosion and death or injury could likely be held liable in a lawsuit situation. It's just all food for thought when replacing these items on our boats. It just doesn't pay to take a chance for a hundred or even a few hundred bucks. And don't be lulled into thinking open engines are exempt from problems. Like the others have pointed out, fuel vapor sinks and collects. Consider no wind, a fuel leak, and hitting that automotive starter you just got from Pep Boys for $50...if there's enough vapor collected it's adios boat, along with anyone and anything close by.