A Few Words on Carbon Monoxide from Boat Exhausts

Carbon monoxide (CO) is an odorless gas that is a combustion by-product of both gas and diesel engines. When inhaled by the human body it is dangerous because it interferes with the blood system and the brain. In small doses it may only result in temporary illness but in larger doses it can progress to brain damage with possible internal hemorrhaging and even death. The first symptom of CO poisoning is drowsiness and sometimes nausea, the later of which is most often associated with diesel produced CO.

CO by itself is odorless, but you can always be sure that it is present by the smell of engine exhaust. In fact this is the best way to detect CO but over a period of time people can become intolerant to the smell and cease noticing it. CO is heavier than air and will tend to collect in lower areas of the hull especially cabin spaces and sleeping quarters.

The most common method by which CO accumulates in cabin spaces is via leaking engine and generator exhaust systems. All exhaust systems need to be inspected frequently. Like on your car, they don’t last forever and require maintenance. All inboard engines both gas and diesel have water cooled exhaust systems. Any time the exhaust system shows evidence of a water leak, there is a serious potential for a CO leak therefore if it’s leaking water, it’s probably leaking CO.

Boats are also somewhat prone to what is known as the “station wagon effect”. When the vessel is moving under engine power a vacuum is created behind the boat, which can actually draw the fumes on board and into the cabin. This can occur at speeds as low as four or five knots. Even though this can’t always be prevented ensuring that all windows and hatches are open keeping the cabin well ventilated is the best insurance. Also sometimes a slight course change which can alter the wind direction can help as well.

The amount of CO produced by a diesel engine is less than half that of a gasoline engine but it is still dangerous.  With diesel you are also being subjected to poisonous sulfur dioxide which is considerably less deadly, but it has a tendency to make you feel sicker. In rough water, it can increase the effects of, and often cause sea sickness. Long term exposure to diesel exhaust can do the same thing as short term exposure to gas exhaust. In either case, the condition has to be eliminated.

The installation of CO alarms in cabins is a good idea and they do work but like anything else they need to be maintained and kept in good order to be effective. Most surveyors that I know recommend their installation as part of a survey report and in reality it is just good common sense. They have become pretty much commonplace in our homes so why not out boats. The largest problem with alarms is that they are very sensitive to contaminants and when they do become contaminated they usually sound and then are disconnected and rendered inoperative.

The good news is that by simply being alert to the potential of the risk you can reduce the odds of this happening to you to nearly zero.


Reprinted From “The Seaworthy Surveyor” Ontario Sailor Magazine

Original Article By David Sandford AMS®

Capacity Calculation for a Marine Starting Battery

I was asked how to determine the battery size (capacity) for a typical engine starting battery. To that end I have come up with some information on how to do just that.

Starting Battery Ratings: Marine Cranking Amps (MCA) or Cold Cranking Amps (CCA). 1 CCA = 1.3 MCA. The ratings are calculated by the same process just at different ambient temperatures.

Minimum Size for Starting Battery: Engine Displacement (in cubic inches) X 2 (Cranking Requirements) X4 (Reserve Capacity) = Required Battery Size (CCA)

I should note that this calculation will give you the minimum size requirement for a starting battery and I sure won’t hurt to increase the size somewhat. I an also a fan of using a deep cycle rated battery as your starting / reserve.

Waking Up (charging) Dead Marine Batteries

Just in case you’ve been a little negligent in battery maintenance over the winter and your batteries won’t charge try this…… Plug the boat in and turn the battery switch to “Both” to connect both banks if you have more than one. Then turn on a passive DC appliance such as the cabin lights and put a load on the system with the charger energized. Leave it for a couple of hours and this just might kick start the battery charger. Once the charger starts you can turn the lights off and let the battery charge as you normally would.

Since a dead battery has no internal resistance and offers little or no load on the charger, loading the system in this way might just be enough to get the charger going. Most chargers need to see a small load in order to initiate.

By the way if this doesn’t work you’re going shopping.

Ethanol in Gasoline as a Marine Fuel

These past few years there has been a lot of scuttlebutt surrounding the use of Ethanol in gasoline sold for marine use. Ethanol (ethyl alcohol) is the same type of alcohol found in booze and is produced agriculturally from crops such as potatoes, sugar cane and corn. In North America it is common to find ethanol levels up to 15% in commercially available gasoline.

Ethanol has three characteristics which as boaters we need to be aware of:

  • Ethanol is more corrosive that gasoline. It can attack aluminum engine fuel system components and it can be very damaging to many types of rubber, neoprene and yes even fiberglass. Since boats, in many cases have a much longer service life than cars, a large number of boats in use today were manufactured before ethanol was even considered as a motor fuel component and as such, engines and fuel systems are susceptible to its corrosive effects. This includes carburetors, fuel injectors, fuel pumps, neoprene fuel lines and tank fill hoses, fiberglass fuel tanks and any other component that is used to convey fuel.
  • Ethanol is Hygroscopic. As we learned in a past post about fiberglass hull construction, hygroscopic means that it can absorb water. This can affect its corrosiveness and with water being a conductor of electricity can make static electricity build up at the filler neck even more of an issue.
  • Ethanol when added to gasoline severely shortens the fuel’s “shelf life”. In many areas due to the onset of winter weather boats are hauled out and dry stored for 6 months every year. In these scenarios a fuel’s shelf life becomes an important issue.

So what does this mean for us boaters? Let me start by saying that the automotive world has largely adapted to these changes and cars and trucks available today are “ethanol friendly” and are for the most part immune to the potentially damaging effects of ethanol gasoline. Also cars and trucks are generally not stored for months on end so a fuels shelf life is usually not an issue.

The next question is, as a boater how do I know if a fuel contains ethanol or not. It “should” be noted on the gas pump in plain view but be careful, it may not be and depending on the area that you’re in it may not even be required. There’s a great website that I highly recommend that you visit if you wish to re-search this further. It is www.pure-gas.org.

Now let’s suppose thatif  your boat resides in an area where it is impossible to obtain ethanol free fuel, let me offer a few tips.

  • Of course first the obvious. Try and use ethanol free fuels whenever possible. The best way to counteract the effects of ethanol is by the use of a quality fuel additive. There are many on the market and I suggest that some fairly extensive re-search is in order.
  • Since neoprene is used extensively on boats for fuel lines and fill hoses and the only types of neoprene that are ethanol resistant are USCG Type A1, A15 and A2. ABYC recommends that A1 and A15 are the only types to be used as fuel supply lines and A2 is the only type recommended as a tank fill hose I highly recommend that you replace any lines and hoses that are not of the above types.
  • If your boat is fitted with a plastic or Marelon deck fuel fill fitting I recommend that it be replaced with a metal one and that it be grounded (connected with a wire) to the remainder of the on board metallic fuel system components. This will allow you to equalize the fuel’s static electrical current build-up by touching the fill nozzle to the grounded fitting. Plastic fittings do not allow for this
  • Don’t forget about you outboard motoes and gensets.

That’s the basics for now but since this is a very hot topic I will no doubt be posting on this subject again as we move forward. Consider this: Since we have now figured out how to “grow” gasoline I would expect the levels of ethanol in fuel to increase rather than decrease.

Stay tuned!

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