Your KE7 most likely had or has the cam plate and rod off the butterfly to control both the butterfly and spark advance with the Spark Lever.
You can remove the parts for the butterfly and set-up the butterfly for the Keller throttle. Then advance the Spark separately. For non-racing applications it would be best to start the motor with the spark in the start position..... this will be easier on the rewind starter. Then after the motor starts, advance the spark, and turn around to advance the throttle to get the boat on plane.
B&M and Tom Cronk have the parts to do this, I think.