Last week in an article about CO from gas engines we published that CO levels in exhaust for fuel injected engines is lower than for carbureted gas engines. Reinhard Burk, Director, MerCruiser Product Engineering, called to say that there is no significant difference in the levels of CO produced by either type of engine. The big difference, he said, comes from gas engines with catalytic converters, such as the new line that MerCrusier has recently produced to meet new California Emission requirements.
Reinhard Burk said that a typical gasoline marine engine, say a 5.0 L unit, produces about 70,000 ppm (parts per million) of CO if one measures it at the hub. With MerCruiser’s new catalytic converter the CO at the hub is about 700 ppm, or about 99% less. Burk said a rule of thumb is that the propagation of CO from the hub to the helm if the boat were standing still and there was no wind, would be diminished by a factor of 10, or theoretically be about 70 ppm. With the boat moving it would be far less, if any.
Actual CO testing conducted recently by MerCruiser’s staff on a 40’ express cruiser with the company’s new catalytic converter, revealed no detectable levels anywhere on the boat, including on the swim platform.
Another side benefit of the engines with catalytic converters is 3% to 5% better fuel economy all the way up the rpm range to about 80% of WOT. Burk said that at WOT fuel consumption was the same.
Burk seemed particularly proud of the fact that MerCruiser engines fitted with the new catalytic converters produced the same horsepower as the engines did in the first place. “We completely re-engineered our exhaust systems to eliminate the effects of the added back pressure due to the catalytic converter,” said Burk. “We have lost no horsepower.”