Re: vintage mercury restore
The KF7 was somewhat of a "bridge" motor between the original 20-cubic inch KE7 and the ultimate "sleeper" motor, the KG7. The KE7 Lightning was introduced in 1947 and was rated at 10hp at 4000 RPM. However, it was shipped with a propeller that would allow it to rev over 5000 RPM on a light hull, at which point the motor was pushing 14 +/- horsepower. The KE7 was a great little motor, but it did need a little refining. The KF7 Super 10 Lightning had some of these refinements, among them a slightly heftier lower unit and heavier connecting rods. The KF7 ran about 15hp.
The KG7 Super 10 Hurricane was further refined with the addition of two more reeds per cylinder on the reed block, and larger intake and exhaust ports. The KG7 pushed close to 17-18hp and was still referred to as a 10 in literature. Anyone who has grabbed the tiller on one of these on a light aluminum boat can tell you there is nothing like it. The last evolution of the KX7 series was the KH7 Super 10 Cruiser, which had the KG7 powerhead mounted on a full gearshift lower unit with a twist grip throttle. The KH7 (1952) evolved into the Mark 20 (1953), which added streamlined cowlings and an extegral fuel tank.
It is possible to upgrade a KF7 to KG7, but it requires some machining and parts swapping. Would be easier to find a KG7 powerhead and swap it over in its entirety and keep the KF7 powerhead for posterity, particularly if the motor is in particularly nice shape. All of the 20-cubic inche powerheads will interchange with a minimum of modifications as they share the same bolt pattern, water tube placement, and driveshaft height. That means you can use a later Mark 20 or Mark 25 powerhead on your KF7 lower unit as well.
Parts, manuals, parts list, etc. can be had at oldmercs.com.
- Scott
