The Dometic SeaStar HH5271 (1.7 cu. in.) helm pump is an axial piston pump designed for manual hydraulic steering. A parts diagram of this unit typically illustrates three main categories of components: the external mounting hardware, the front-facing seal assembly, and the internal pump core. Core Components of the HH5271 Diagram
An exploded view reveals how the steering wheel connects to the internal hydraulic mechanism. Major parts usually identified include: Shaft & Drive Components:
3/4" Tapered Shaft: The main drive point for the steering wheel.
Woodruff Key: A semi-circular key that locks the steering wheel to the shaft to prevent slipping. Seastar Hh5271 Parts Diagram
Nyloc Nut (5/8"-18): Secures the steering wheel onto the shaft. Seal Assembly (Front Mount):
Shaft Seal (Quad Ring): A critical failure point that prevents fluid from leaking out of the shaft opening.
Top Cover & Screws: The exterior plate that holds the shaft seal in place. Internal Pump Assembly: The Dometic SeaStar HH5271 (1
Axial Pistons: Usually 7 or more pistons that move fluid when the shaft is rotated.
Roller & Ball Bearings: Support the rotor and piston race for low-friction operation.
Lock Valve & Relief Valve: Internal safety mechanisms that prevent "kickback" from the engine and protect the system from over-pressurization. Common Service and Repair Kits What is the Seastar HH5271
Most "diagram" searches are initiated to identify parts for the HP6032 Helm Seal Service Kit, which is the most common repair package for the HH5271. Included in HP6032 Kit Quad Ring Seal Prevents fluid leaks at the steering shaft. Woodruff Key Locks the steering wheel to the pump shaft. Top Cover Protects the seal and houses mounting screws. Nyloc Nut Final fastener for the steering wheel. ORB Fittings Connects hydraulic lines to the back of the helm. No (Standard with HH5271-3/4) Evolution: HH5271 vs. HH5271-3 SeaStar Hydraulic Helm Pump HH5273 rebuild
The Seastar HH5271 is a balanced hydraulic helm pump. It is typically used in single or dual-station steering systems for boats ranging from 18 to 38 feet (depending on cylinder size). This helm pump converts the rotational motion of the steering wheel into hydraulic pressure, which then moves the outboard engine(s) or rudder.
Key Specifications:
If you are looking for the most common repair items, you will likely need:
The official Dometic/Seastar parts diagram for the HH5271 is typically found in the "Seastar Helm Kits" section of their service manual (Technical Data Sheet 296225). The diagram will show an exploded view of the helm body.
