I'm sorry about not understanding (older model Johnson). When you said older model, you meant what Noah used on the Ark. I have looked through my books and it is hard to find a SYN grease for your application (GEARS). The grease you are using now is designed for bearings and slides. (Lightly loaded. What ever you choose, make sure it is compatible with the calicum thickener you are using now, or do a complete flush of your housing. Calicum is not compatable with most other thickners. That is outstanding you have these old of motors and still running.