You should be able to check this out yourself. Go to this website: epc.brp.com. This is the original factory exploded parts diagrams for all their engines. Get into the Johnson outboards and go thru the 70 hp parts lists one at a time. Compare the parts on your engine with those from each year's engines. Keep in mind that things like the heads have part numbers on them that probably compare to the factory parts lists. You will find a lot of similarities between all of these 3 cylinders. A fairly standard engine. Differences are in the things like the ignition parts, carbs/linkages, choke systems and power trim systems. Later models had a trim switch on the lower cowling, in addition to the one on the control box handle. Somewhere around 1991, the blocks were reconfigured from 49 cubic inches to 56. This larger displacement made a huge torque improvement in these engines.
