ATF has a lot of detergents to keep your transmission clean plus a lubricant for the bushings. The highly volatile acetone will get it into the crevices. It works as well as products costing three times as much. Heat and cold uses the different expansion rates of iron and aluminum to break the bond between the two. The high pressure grease works well if you can seal off the ports. This can be difficult in four cylinder (double apposed) outboards, especially Johnsons which use a ported piston. Remove the cylinder nuts and work on the piston with the closed ports to gain access to the connecting rod screws. high pressure grease has been known to break out thin places the cylinder wall. this is less likely in cylinders with removable heads because the casting sand has more support and is less likely to shift.
