While the CO produced by a gas-fueled propulsion engine is of concern, the motion of the boat aides significantly in dis-persing the exhaust,diluting the CO content of the air on the boat to generally acceptable levels.Exceptions to safed ispersal occur most often when the engines are left idling for long periods of time to charge batteries or if the stationwagon effect (negative pressure area behind a moving boat) draws the exhaust into the cockpit or into an interior compartment.In most cases,though,the great-est risk from CO poisoning comes from running theboat's genset at anchor or in the slip,eliminating the dispersal effect of the boat's motion. In fact, as documented in numerous accident and coroner's reports, the CO content of the exhaust from a genset on a boat may not harm anyone on that boat.On the other hand, it is sufficient to cause illness or death on a nearby boat that's accidentally immersed in the genset's exhaust plume.

A few facts about the mechanism with which CO can injure or kill us provide a useful measure of the risk.Our lives depend on the ability of our respiratory system to deliver oxygen to the hemoglobin, the oxygen carrier in our blood. Under normal conditions, the hemoglobin absorbs some of the oxygen from the air we breathe and then distributes it to our cells. Hemoglobin,however, has as much as 210-250 times greater affinity for CO than it has for oxygen.The technical term for the condition in which the hemoglobin carries CO in preference to oxygen is carboxyhemoglobin. The cumulative effect of exposure to CO exacerbates the problem.The hemoglobin hangs on to whatever CO it attracts. Depending on the physical condition of the person exposed to the CO (the most sensitive can be those who are physically active, very young, very old and anyone with under-lying health problems), even very small concentra tions of CO can be hazardous. For example the EPA's National Ambient Air Quality Standard (NAAQS) for CO sets a limit of nine parts per million for eight-hour exposure and not more than 35 ppmfor a one-hour average.

  That's not happening for several reasons. First, the industry quickly saw the writing on the wall years ago and immediately got very busy developing engines that meet (and in some cases exceed) the 2006 requirements. Second, since the regs are for fleet averages, engine makers can afford to keep their dirtier 2-strokes in the mix as long as there is a viable market for them. But if you are a fan of the older 2-strokes, do not assume that because they are still being offered in 2006 they will be around forever. At some point, each and every one will, without warning, wander off into outboard limbo as a DI 2-stroke or 4-stroke replacement comes down the line.

It should be clear beyond any doubt that protecting ourselves and others from CO poisoning will require us to run the genset only during a gale, extend its exhaust pipe to the height of the main mast on a good-size sail-boat or rely on the manufacturers to significantly reduce the amount of CO in the exhaust-the only sensible approach.

Westerbeke Corporation,producer of a large percentage of all gasoline fueled gensets, has tackled the problem and achieved remarkable results,reducing the COemissions of its new Safe-CO gensets by more than 99 percent when compared with typical carbureted andfuel-injected units.Westerbeke addressed the CO problem in two ways: A precise electronically controlled fuel-injection system minimizes the CO content of the exhaust, and a catalytic converterreacts with the CO to ultimately achieve a safe CO level in still air.

Although the company's methods parallel those of the automotive industry, dealing with the extreme heat at which catalytic converters function challenged the engineers. Westerbeke solved the hot converter problem by encasing it in stainless steel and housing it within the engine's water-cooled exhaust manifold. As a result of their efforts, the exhaust of the SAFE-CO genset typically contains only 200 parts per million (ppm) of CO when the converter has reached its operating temperature. The real-world value of this achievement was demonstrated in a series of tests conducted by NIOSH(National Institute for Occupational Safety and Health) on houseboats equipped with the SAFE-CO gensets. The well-documented tests showed that the CO levels were less than 10 ppm anywhere on the vessels.

The report included data taken from a Westerbeke genset that had been retrofitted with an after-market fuel-injection system. The results, although excellent at less than 1,000 ppm, were five times higher than that achieved with the factory engineered system. The extra margin afforded by the system Westerbeke is using provides insurance against the inevitable changes in performance that occur as the genset ages. The testing program included checks of CO level as the load on the genset was varied, as well as the initial levels.

Kohler has made similar strides with its line of low carbon monoxide units. The new 5ECD and 7.3ECD models are on the market now. After a series of tests similar to Westerbeke, they have been able to reduce CO emissions by 99 percent. The carburetor has been replaced by a computer- controlled engine that uses electronic fuel injection.

Keeping the Safe-CO genset safe requires normal routine maintenance, plus a recommended check of the CO level at 1,000 hours. This test can be done using the same CO measurement device employed at auto service shops. The converter has a recommended service life of 2,000 hours, but that replacement interval may be increased as additional field service experience is accumulated. Pay particular attention to the design, installation and maintenance of the exhaust system, particularly if the genset is installed below the boat's load waterline, using a water-injected exhaust system. The inside of the converter MUST remain dry, so avoid any chance of filling the exhaust with water (as can happen during continued unsuccessful attempts to start the genset with the cooling water seacock open, or in the event of a failure of an antisiphon valve).