- 1973 – 1st year of JS 400
- WSAA hull (Normal, flat bottom JS hull)
- WSAB hull (Commonly called V-hull)
- See here for photos & info regarding early JS400 features
- 1974-1975 JS 400
- 1977-1981 JS440
- Full Circle crankshaft
- 17 Head studs
- Aluminum cylinder
- Large electrical box
- 1982-1989 JS440
- T-bone crankshaft
- Cast iron cylinder
- Smaller 550 style electrical box
- 1990 JS440
- Rear exhaust
- 1991-1992 JS440
- 1 piece teal motor mounts
- Silver painted engine
JS400/440 Model Updates
