SeaStar HC5345-3 Steering Cylinder: Fitment & Replacement – PartsDuck.com

Quick answer: The Dometic SeaStar HC5345-3 is a standard front-mount outboard hydraulic steering cylinder with an 8-inch stroke and 8.34 cu. in. displacement. It is widely used, but replacement fitment must be verified against the exact engine and Dometic application instructions.

SeaStar HC5345-3 Specs

Dometic’s front-mount cylinder documentation lists:

Front-mount pivot configuration
8-inch stroke
8.34 cu. in. displacement
Adjustable ORB cylinder fittings

Shop SeaStar HC5345-3 →

What Boats and Engines Does It Fit?

This is where accuracy matters most. Do not treat HC5345-3 as a universal "SeaStar cylinder."

Dometic's current installation manual covers HC5345-3 and several closely related cylinders and provides engine/application-specific assembly diagrams. Confirm the exact outboard make, model, year, tilt tube arrangement and mounting geometry before ordering.

HC5345 vs. HC5345-3

Owners often search older SeaStar numbers without the current revision suffix. When replacing an older cylinder, use the latest Dometic cross-reference/application information rather than assuming that adding "-3" makes it a direct replacement in every installation.

Check the hose ports: HC5345-3 uses ORB fittings. NPT fittings are not interchangeable with these ports.

Related SeaStar Components

A complete steering system may also require:

Compatible SeaStar helm
Correct SeaStar hoses/tubing
Fittings and service parts
Dometic-approved hydraulic fluid
Application-specific engine mounting hardware

Can You Rebuild or Reseal a SeaStar Cylinder?

Some steering cylinders can be serviced with the correct Dometic service parts and procedures, but not every leaking or worn cylinder should automatically be resealed.

Inspect for shaft damage, corrosion, worn mounting points, damaged threads, excessive play and other structural problems. If the hard parts are damaged, replacement may be more appropriate than a seal-only repair.

Jack Plate Clearance

This is a critical installation point. Dometic's current HC5345-series instructions warn installers to check for interference between the jack plate and steering cylinder. Interference may occur during full tilt, and Dometic notes that lift restrictors/tilt-stop solutions may be required in some installations.

Clearance should be checked throughout the full steering and trim/tilt range before operation.

Installation Is a Steering-Safety Job

The Dometic manual includes specific torque requirements, bracket orientation, tiller-bolt procedures and maintenance checks. Those details should come from the current installation instructions, not a generic blog article.