Merc 25 HP #6185448 -- Have document on timing that says: First (1)(full throttle, motor in test tank), adjust spark advance linkage to align 3 dots (on flywheel)with reference mark. Second (2) (full throttle, motor in test tank), rotate throttle cam to align cam mark with throttle roller. Then lengthen or shorten throttle linkage to align 2 dots with reference. [Comment: real scary doing this in my yard.] Question 1: Can I practice this with prop off (no load) using a flush, and how close might I come. Question 2: Won't the throttle cam and throttle linkage effect (1) at first trying to get 3 dots for spark advance? [Comment: the 3 dots are way to the left, adjustment in the spark advance linkage is as far as it can go - none left.]<br /><br />Help?