Couple of things to note, one, the process you use was replaced by the timing tool as it was determined to be a far better approach to setting the timing. Also the tool that works for your motor, also works for motors between the 5-20 hp range including the souped up "25"hp which were 20 hp blocks. After a period of time OMC started incorporating the timing marks on the flywheel simulating the timing tool, to match up with the marks on the plate so one would not have to remove the flywheel at all to set the timing correctly.