I have a 1997 Mercruiser 5.7L 2brl / Alpha, which has "Thunderbolt V" proudly displayed on flame arrestor cover. One of the big differences between Thunderbolt IV an V was the addition of anti-knock system. On close inspection this last week, I don't have a anti-knock module, or a anti-knock sensor. I couldn't find any elec plug or disconnected wires, and from all indications, it came this way from the factory. The service manual does not mention anything about the anti-knock being an option.<br /><br />Assuming it did indeed come this way from the factory, was the anti-knock not used on carb systems? or was this possibly an economy version of this engine? Thanks for any input.
