A KF7 is kinda the odd duck of the 20-cube green tanker motors as it was an intermediate between the first gen KE7 and the king of the hill KG7. It had some of the improvements of the KG7 (slip clutch prop) with the performance restrictions of the KE7 (small ports, two reeds per cylinder). It was rarely used in racing and was never offered as a racer from the factory. That said, someone likely mated your powerhead to a quicksilver unit.
Question, does your motor have the matching mid-section? The mid came in two flavors, the "Q" length tower for 15-inch transom, which is identifiable by having two AV plates, or the "H" length tower, which was for 12-inch transoms and had only a single AV plate. A good Quicksilver gear foot can command a decent price between $500 and $1000 depending on who wants one badly enough. Being that it is not original to the KF7, it probably isn't much more valuable if it comes with the motor or not. If you're planning on getting rid of it, it might be worth more selling separately than together... But, the market (.ie eBay) can be fickle.
