Crush plates, prop extensions and prop bolts all have to match your engine’s propeller flange. Most flanges use one of the SAE patterns below. Find yours by checking the bolt size, the bolt circle and the drive lug diameter.
| SAE | Bolt Size | Bolt Circle | Lug Diameter | Common Engines* |
|---|---|---|---|---|
| SAE #1 | 3/8″ | 4.375″ | .625″ | C-65, C-85, C-90, O-200, O-235 |
| SAE #2 | 3/8″ | 4.75″ | .625″ | O-235, O-290, O-300, O-320, O-340 |
| SAE #5 | 7/16″ | 4.75″ | .625″ | O-320, O-340 |
| SAE #6 | 1/2″ | 4.75″ | .75″ | O-340, O-360, C-375, O-540, O-720, 4-cyl C-360 |
| Rotax 912/914/915/916 | 8mm | 4″ (101.6mm) | .500″ | 912, 914, 915, 916 |
| Rotax 912 (pre-1997) | 8mm | 100mm | .500″ | Early 912 |
| Rotax 2-stroke | 8mm | 75mm | No lugs (1″ center bore) | 447, 503, 582 |
How to check your flange
- Bolt circle: measure from the center of one bolt hole straight across to the center of the opposite hole.
- Bolt size: the diameter of your prop bolts (3/8″, 7/16″ or 1/2″).
- Lug diameter: the outside diameter of the drive lugs (bushings) pressed into the flange.
Not sure, or running something else? We make parts for ARP 502/883, Franklin, Continental and other flanges too. Call or text (817) 326-6293 or request a quote and we’ll get you the right part.