NOTE: Muncie – Neptune models having a “U” in their model designation had under water exhausts . Example: OB2AU
| Model Name: 1931 OB15A Muncie Master | |
| Original carburetor | Tillotson MS-47A |
| Magneto | Eisemann Model 82D |
| Cylinders | 2 |
| B x S | 2 1/2” x 2″ |
| HP | 16 |
| Point gap | 0.020 |
| Sheer pin | 5/32” x 3/4” or 3/16” x 3/4“ |
| Oil | 2/3 pt. SAE-30 per Gal. |
| Tank | Sheet aluminum |
| Exhaust | Under water |
| Lower unit | Ball bearing |
| Rope plate | 6″ Muncie twin |
| Model Name: 1931 OB2 Muncie | |
| Original carburetor | Tillotson MS-45A |
| Magneto | American Bosch Model FY6-ED2 |
| Cylinders | 2 |
| B x S | 2″ x 1 1/2“ |
| HP | 2 1/2 |
| Point gap | 0.020 |
| Sheer pin | 5/32” x 3/4” or 3/16” x 3/4“ |
| Oil | 2/3 pt. SAE-30 per Gal. |
| Tank | Cast hammered aluminum |
| Exhaust | Above water |
| Lower unit | Plain bearing |
| Rope plate | 6″ cast aluminum |
| Model Name: 1931 OB2A Junior Neptune | |
| Original carburetor | Tillotson MS-45A |
| Magneto | American Bosch Model FY6-ED2 |
| Cylinders | 2 |
| B x S | 2″ x 1 1/2“ |
| HP | 2 1/2 |
| Point gap | 0.020 |
| Sheer pin | 5/32” x 3/4” or 3/16” x 3/4“ |
| Oil | 2/3 pt. SAE-30 per Gal. |
| Tank | Cast hammered aluminum |
| Exhaust | Above water |
| Lower unit | Plain bearing |
| Rope plate | 6″ Neptune cast aluminum |
| Model Name: 1931 OB2C Motorgo | |
| Original carburetor | Tillotson MS-45A |
| Magneto | American Bosch Model FY6-ED2 |
| Cylinders | 2 |
| B x S | 2″ x 1 1/2“ |
| HP | 2 1/2 |
| Point gap | 0.020 |
| Sheer pin | 5/32” x 3/4” or 3/16” x 3/4“ |
| Oil | 2/3 pt. SAE-30 per Gal. |
| Tank | Cast hammered aluminum |
| Exhaust | Above water |
| Lower unit | Plain bearing |
| Rope plate | 6″ cast aluminum |
| Model Name: 1931 OB2CB Muncie Twin | |
| Original carburetor | Tillotson MS-45A |
| Magneto | American Bosch Model FY6-ED2 |
| Cylinders | 2 |
| B x S | 2″ x 1 1/2“ |
| HP | 2 1/2 |
| Point gap | 0.020 |
| Sheer pin | 5/32” x 3/4” or 3/16” x 3/4“ |
| Oil | 2/3 pt. SAE-30 per Gal. |
| Tank | Cast hammered aluminum |
| Exhaust | Above water |
| Lower unit | Plain bearing |
| Rope plate | 6″ cast aluminum |
| Model Name: 1931 OB2D | |
| Original carburetor | Tillotson MS-45A |
| Magneto | American Bosch Model FY6-ED2 |
| Cylinders | 2 |
| B x S | 2″ x 1 1/2“ |
| HP | 2 1/2 |
| Point gap | 0.020 |
| Sheer pin | 5/32” x 3/4” or 3/16” x 3/4“ |
| Oil | 2/3 pt. SAE-30 per Gal. |
| Tank | Cast hammered aluminum |
| Exhaust | Above water |
| Lower unit | Plain bearing |
| Rope plate | 6″ cast aluminum |
| Model Name: 1931 OB4A Improved Twin | |
| Original carburetor | Tillotson MS-45A |
| Magneto | Eisemann Model 82D |
| Cylinders | 2 |
| B x S | 2″ x 1 1/2“ |
| HP | 4 |
| Point gap | 0.020 |
| Sheer pin | 5/32” x 3/4” or 3/16” x 3/4“ |
| Oil | 2/3 pt. SAE-30 per Gal. |
| Tank | Cast hammered or smooth |
| Exhaust | Under water |
| Lower unit | Plain bearing |
| Rope plate | 6″ Muncie |