OMC Powerhead on a Bayer 15 inch tower with a Mercury 20H short skeg gear case.  Electronic ignition with cut down lightened flywheel. All aluminium exhust stack and elbow. We have not check ratio but believe it to be 1:1.  Purchased from the John Snell collection, we have been told these were fast engines. We believe it may the engine that Rusty Sitton ran through the kilo traps at 83 MPH.