Sierra V-Belt 18-15520 Replaces Mercury Marine 57-33170 for MerCruiser 4.3L 175/185 HP Stern Drive

The Sierra V-Belt 18-15520 is a replacement accessory drive belt engineered for MerCruiser 4.3L 175/185 HP stern drive engines built with the 262 cid, 6-cylinder block. It is constructed from a rubber compound reinforced with high strength synthetic cords, a design intended to resist shock loading while keeping stretch to a minimum so belt tension and pulley alignment stay consistent over the belt's service life. The special rubber compound section is formulated to transfer load forces smoothly and evenly to the internal cords, reducing the slipping and glazing that shorten the life of a lower quality belt.

This is a standard V-belt profile (not serpentine), sized with an effective length of 52 inches and a top width of 29/64 inch (11.5 mm). It fits MerCruiser 4.3L 175/185 HP engines from the 1985-92 model years, within engine serial number range A331455 through D714106, and cross-references to Mercury Marine and OMC stern drive part numbers. Replacing a cracked, glazed, or stretched accessory belt with this part restores proper alternator, water pump, and power steering pulley drive on the applicable engine.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-15520
• Belt Type: V-Belt
• Effective Length: 52 inches
• Top Width: 29/64 inch (11.5 mm)
• Item Dimensions: 52 inches long x 0.64 inch wide
• Material: Rubber
• Weight: 0.29 pounds
• UPC: 030999566690

Fitment

• MerCruiser 4.3L 175/185 HP stern drive engines, 262 cid, 6-cylinder, 1985-92, engine serial number range A331455 - D714106

Replaces (OEM)

• Mercury Marine 57-33170
• Mercury Marine 57-33170Q
• Mercury Marine 57-37619
• Mercury Marine 57-37619Q
• Mercury Marine 57-37619T
• OMC 912714
• Mallory 9-55001

Frequently Asked Questions

What engines does the Sierra 18-15520 V-belt fit? This belt fits MerCruiser 4.3L 175/185 HP stern drive engines with the 262 cid, 6-cylinder block, built within engine serial number range A331455 through D714106, covering the 1985-92 model years.

Is 18-15520 a V-belt or a serpentine belt? Sierra part 18-15520 is a standard V-belt profile, not a serpentine belt, with an effective length of 52 inches and a top width of 29/64 inch (11.5 mm).

What OEM part numbers does this belt replace? The Sierra 18-15520 cross-references to Mercury Marine 57-33170, 57-33170Q, 57-37619, 57-37619Q, and 57-37619T, as well as OMC 912714 and Mallory 9-55001.

What material is the 18-15520 V-belt made from? It is made from a rubber compound reinforced with high strength synthetic cords, a construction meant to resist shock loading and keep stretch low over the belt's service life.

How much does the Sierra 18-15520 V-belt weigh? This V-belt weighs 0.29 pounds.

What are the dimensions of the 18-15520 belt? The belt measures 52 inches long with a top width of 29/64 inch (11.5 mm); overall listed item dimensions are 52 inches long by 0.64 inch wide.

Will this belt fit an OMC stern drive as well as a MerCruiser? Yes, in addition to its MerCruiser 4.3L 175/185 HP fitment, the 18-15520 cross-references to OMC stern drive part number 912714.

Is the Sierra 18-15520 a genuine OEM belt or an aftermarket replacement? The 18-15520 is a Sierra-branded aftermarket replacement belt engineered to the same fit and function as the Mercury Marine and OMC part numbers it replaces.

What is included when I order part 18-15520? Each order includes one Sierra 18-15520 V-belt; no pulleys, tensioners, or hardware are included.

How do I know if my engine's serial number is within the fitment range for this belt? Check your engine's serial number plate against the range A331455 through D714106; if your MerCruiser 4.3L 175/185 HP engine falls within that range, the 18-15520 is the correct belt.

Why would a boat owner need to replace this V-belt? Accessory drive belts like the 18-15520 stretch, crack, or glaze over time from heat and flexing, which can cause slipping at the alternator or water pump pulleys, so periodic replacement with 18-15520 keeps the drive system operating correctly.