The most important factor in determining what Autopilot to buy is knowing the hydraulic displacement of your boats steering system. To find out this information you will need a physical inspection of your steering system. If this proves to be difficult, call your boat's manufacturer with your vessel hull number and they will provide the needed information.
You need to know:
- Steering System Manufacturer
- Steering Cylinder model #
- Do you have 1 or 2 Steering Cylinders (or more?)
- Do you have engine assisted hydraulic power steering?
Refer to the charts below (Table 1.1) to find your steering Cylinder Hydraulic displacement.
Table 1.1
Hydraulic Cylinder Capacity
| Hynautic | | Wagner |
| Cylinder Model No. | Disp. Cu. In. | Cylinder Model No. | Disp. Cu. In. |
| K1 | 12.1 | N65 | 6.0 |
| K2 | 17.6 | N85 | 7.8 |
| K3 | 23.1 | N40-120 | 7.7 |
| K4 | 30.5 | N40-190 | 12.2 |
| K10 | 7.5 | N50-190 | 19.1 |
| K11 | 11.8 | N50-300 | 30.2 |
| K12 | 8.6 | N80-190 | 49.0 |
| K13 | 11.0 | N80-300 | 77.3 |
| K14 | 8.6 | N175-750 | 14.6 |
| K16 | 7.0 | N175-1000 | 19.6 |
| K17 | 9.0 | N250-800 | 33.0 |
| K18 | 8.3 | N250-1000 | 41.5 |
| K19 | 9.0 | N250-1300 | 53.6 |
| K20 | 8.3 | N350-1200 | 94.0 |
| K22 | 13.3 | T-2 | 9.9 |
| K24 | 6.6 | T-3 | 23.0 |
| K25 | 13.3 | T-4 | 31.2 |
| K26 | 16.0 | T-5 | 41.8 |
| K27 | 13.3 | T-10 | 54.5 |
| K28 | 16.0 | T-11 | 54.5 |
| K29 | 16.0 | T-12 | 76.7 |
| K31 | 25.5 | T-12B | 92.0 |
| K32 | 20.0 | T-13 | 76.7 |
| K33 | 23.0 | T-13B | 92.0 |
| K9 | 55.0 | | |
| K8 | 39.2 | | |
| Teleflex | | Marol |
| Cylinder Model No. | Disp. Cu. In. | Cylinder Model No. | Disp. Cu. In. |
| BA125-7 | 7.2 | MRB-30 | 4.6 |
| BA135-7 | 8.5 | MRB-50 | 6.6 |
| BA137-7 | 8.5 | MRB-63 | 9.4 |
| BA150-7 | 10.2 | MRB-80 | 24.1 |
| BA175-7 | 13.2 | |
| BA200-7 | 18.9 | Hy-Drive |
| 125-7 | 16.0 | 310 | 9.9 |
| 150-7 | 13.3 | 312 | 6.4 |
| 175-7 | 16.0 | 313 | 11.9 |
| 200-7 | 41.0 | 314 | 18.9 |
| Morse | | Vetus |
| Cylinder Model No. | Disp. Cu. In. | Cylinder Model No. | Disp. Cu. In. |
| 306949 | 7.9 | MT30 | 4.1 |
| 303995 | 8.7 | MT45 | 9.3 |
| 303932 | 6.5 | MT65 | 9.3 |
| 303942 | 11.4 | MT80 | 11.6 |
| 308610 | 13.5 | MT105 | 16.0 |
| | MT140 | 21.4 |
| | OB35 | 6.4 |
| | OB85 | 10.4 |
If you have more than one steering Cylinder you must add the displacement of each steering Cylinder together to get your total hydraulic displacement.
Your total displacement number is then used in the next table (table 1.2) to determine what hydraulic pump you will need. After you determaine which hydraulic pump your boat requires simply choose a system (there are usually several) that uses the required pump.
Table 1.2
Raytheon / Autohelm Maximum Pump Volume
