R2173 Mackay 2922 Dunbier 8" Dogbone Roller Black Poly WITH INSERT | Marine Trailer Part

🔧 Product Description

Mackay Black Poly Dogbone Roller 8 Inch with Aluminium Insert – Part Number: R2173

A black poly dogbone boat-trailer roller designed to support and guide the hull during launching, retrieval and road transport. The profile helps keep the keel or lower hull aligned while the roller turns on the matching shaft.

⚙️ Key Features

• Black Poly construction
• Dogbone support profile
• Designed for repeated marine trailer immersion
• Replaceable independently of a serviceable bracket
• Matched to a defined shaft diameter and bracket width

📏 Specifications

• Approximate roller dimensions: 200 × 55mm
• Centre bore: Approximately 20mm
• Matching shaft: R2191G 20 × 255mm
• Dunbier cross-reference: 2922
• Aluminium reinforcing insert

🔄 Cross Reference & Related Parts

• Mackay: R2173
• Dunbier cross-reference: 2922
• Other roller profiles and materials are not direct replacements unless length, bore, end diameter and hull suitability match

🚤 Trailer Compatibility & Application

• Suitable for fibreglass, painted and other hulls where a resilient or softer contact surface is preferred
• The roller should contact a structurally supported hull area rather than a fitting, strake or unsupported panel
• Confirm bracket width and side clearance before installation

🔌 Function

• Supports the hull and provides a rolling path as the boat moves on or off the trailer.

⚠️ Common Signs of Failure

• Roller is cracked, split, flattened or permanently distorted
• Centre bore is elongated
• Roller does not turn freely
• Material is hardened, softened or UV-degraded
• Hull develops marks from a damaged or contaminated roller surface

🛠️ Installation & Safety

• Support the boat before removing any load-bearing roller
• Use the correct shaft, washers and retention hardware
• Align the roller to share load with adjacent supports
• Confirm free rotation without excessive side movement
• Recheck the complete hull-support setup after replacement

📦 Condition

• Brand new Mackay trailer component
• Supplied as one roller
• Supplied in original or equivalent packaging