Idler Pulley for Murray Scotts Ranch King 38 40 42 Inch 91179, 421409 0091179 091179 91179MA 421409MA 091179MA MY91179

What It Is

This idler pulley is a replacement part for Murray, Scotts, and Ranch King riding mowers with 38, 40, or 42-inch cutting decks. It routes and tensions the mower deck drive belt, keeping it aligned during operation.

Fitment & Compatibility

Before buying, verify these three things:

• Deck size: Fits 38, 40, and 42-inch decks only. Check your deck’s stamped size.
• Model numbers: Compatible with OEM part numbers 91179, 421409, 0091179, 091179, 91179MA, 421409MA, 091179MA, and MY91179. Cross-reference with your mower’s parts diagram.
• Physical measurements: Measure your old pulley’s outer diameter (typically 3.5–4 inches), bore size (usually 1/2 inch), and overall thickness. This part has a steel ball bearing and a smooth outer race. If your original has a different bearing type (e.g., plastic bushing), this is a direct replacement.

Does not fit all Murray or Scotts models—only those using the listed OEM pulley numbers. Check your deck’s spindle pulley pattern; some decks use two identical idlers.

Key Things to Know

• Quality: Steel bearing with sealed ball bearings—more durable than plastic-bushing pulleys common on budget replacements.
• Installation: Easy if you have the right tools. You’ll need a 1/2-inch socket or wrench for the mounting bolt. No special puller required unless the bolt is seized.
• Common gotcha: The pulley spins freely but can be stiff when new. This is normal after a few minutes of run time. If it’s rough or noisy out of the box, return it.
• Belt wear: Always inspect the belt for cracks or glazing when replacing the pulley. A worn belt can cause premature pulley failure.

Should You Buy It

If you need a direct, drop-in replacement for a worn idler pulley on a Murray, Scotts, or Ranch King 38–42-inch deck, this is a solid choice. The steel bearing and positive reviews suggest good value at $15.99. Avoid if your mower uses a different pulley size or if you need a pulley for a 46-inch or larger deck.