SeaStar HK6400-4 Hydraulic Marine Steering Kit

SeaStar HK6400-4 Hydraulic Steering Kit

The Dometic HK64004 SeaStar Hydraulic Steering Kit is the front mount hydraulic steering kit for single non power assisted outboards up to about 300 HP on most fishing, bay, and family boats. It pairs the proven SeaStar front mount helm and the popular HC5345-3 front mount outboard cylinder for smooth, reliable steering on typical outboard applications. It is a great choice for boats that cruise and run at moderate speeds. For high performance bass boats or hulls regularly running above about 60 mph, SeaStar PRO is usually recommended instead.

The updated -4 kit, which is the direct replacement for the HK6400A-3 kits include the new -4 helms redesigned with new valve technology, more durable check valves and a revamped design.

Key Benefits of the HK6400-4 Kit

• Standard SeaStar system for single non power assisted outboards up to approximately 300 HP when installed to SeaStar guidelines.
• Smooth, consistent steering feel and reduced torque steer compared to mechanical cable systems.
• Well suited to everyday cruising, fishing, and family use on most outboard powered boats.
• Balanced front mount cylinder design for even wheel effort port and starboard.
• SeaStar 1.7 cu in helm provides a comfortable number of turns lock to lock with the HC5345-3 cylinder.
• Meets applicable ABYC and NMMA steering standards when installed per SeaStar instructions.

What Is Included in the HK6400-4 Kit

Important: This kit ships without steering hoses. SeaStar hoses must be ordered separately to complete the installation.

Recommended Applications and Limits

Not intended for surfacing propeller applications, race boats, or high performance bass boats that regularly exceed about 60 mph. For those applications, SeaStar PRO is usually the correct choice.

Will This Cylinder Work on My Boat?

Downloads and Resources

Installation Tips

• Confirm that your engine is listed for the HC5345-3 cylinder in the current SeaStar application guide.
• Mount the HH5271-4 helm on a flat, reinforced dash with the correct 3 inch hole and a secure backing plate if needed.
• Route hoses to avoid tight bends, pinch points, chafe, and heat sources. Keep bend radii as large as practical.
• Use only SeaStar approved fittings and hoses rated for SeaStar outboard systems.
• Bleed the system carefully until there is no visible aeration and the wheel feels solid from lock to lock.
• Verify full engine movement port to starboard, correct centering, and that there is no interference at the cylinder or tiller arm.

Maintenance Guidelines

• Check fluid level at the helm periodically and top up with SeaStar hydraulic steering fluid only.
• Inspect the cylinder shaft, seals, and hose fittings for signs of seepage at regular service intervals.
• Rinse the cylinder and fittings with fresh water after salt water use when possible.
• Do not use automotive power steering fluid or ATF. Always use SeaStar specified steering fluid.
• If the wheel develops free play, noise, or a spongy feel, schedule a steering inspection before your next trip.

Frequently Asked Questions

Does this kit include hoses?
No. The HK6400-4 kit includes the helm, front mount cylinder, fluid, and bleed kit. SeaStar hoses are sold separately so you can match your exact rigging length and style.

What is the difference between HK6400-4 and HK7500-4?
HK6400-4 is the standard SeaStar kit for typical outboard boats up to about 300 HP and moderate speeds. HK7500-4 is the SeaStar PRO kit with higher pressure components and a PRO cylinder for high performance hulls and higher speeds.

Can I upgrade from HK6400-4 to SeaStar PRO later?
Yes. Many customers start with a standard SeaStar system and later upgrade to SeaStar PRO components if they increase engine power or speed. Contact us with your current part numbers and we can help you plan the upgrade path.

Can I add a second station?
Yes. You can add a second SeaStar helm, additional hoses, and fittings for a dual station installation, as long as the overall system stays within SeaStar guidelines.

Questions?

• Tech Support: Tech Support Page
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• How to Measure Seastar Hose: Guide
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