The Johnson Service Manual suggests oil type and quantity be checked where poor compression exists. Also, they suggest for working engines, the oil quantity be doubled. Working engines, in this case, means engines subjected to extended usage. Take care to carefully mix these products with gasoline before adding to motor fuel tank. Also, note these oils tend to separate after storage.
Gear cases have an interesting history.
The early bevel gears commonly failed in service. Scoring, galling, corrosion and abrasion, were not controlled. The lubricant, grease, was the cause. Lack of attention, difficult to replace, no protection against metal to metal contact and abrasive impurities were known problems. As engine horse power and RPM's increased, new solutions were found.