Sierra V-Belt 47-15550 — Marine Inboard Sterndrive
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The Sierra 18-15550 is a cogged marine V-belt designed for selected Mercury MerCruiser big-block inboard and sterndrive accessory-drive systems. High-strength synthetic cords resist stretching and shock loading, while the precision-moulded cog profile improves flexibility and allows cooling airflow around the belt. Its specially compounded rubber construction distributes drive loads evenly and maintains positive contact with the pulley grooves.
Key Features
- Marine replacement cogged V-belt
- Effective length: 55 inches / 139.7 cm
- Top width: 29/64 inch / 11.5 mm
- High-strength, low-stretch synthetic cords
- Precision-moulded cogs improve flexibility
- Open cog profile helps control heat buildup
- Rubber edges provide positive pulley contact
- Synthetic-rubber W-profile construction
- Supplied as one replacement belt
Engine Compatibility
Designed for selected Mercury MerCruiser 7.4L/454 cubic-inch GM V8 applications, including certain 330 GM 454 engines from 1982–1987 and 454 MAG Alpha applications from 1986–1989. Additional references associate it with selected 454 MAG Bravo and 7.4L Bravo installations through the early 1990s.
Serial Number Fitment Notice
Confirm the engine model, serial-number range, original belt number and complete accessory-drive arrangement before ordering. MerCruiser 454 and 7.4L engines may use different belts depending on the power-steering system, pulley layout, drive model and production year.
When This Part Needs Replacement
Replace the belt when it develops cracking, glazing, frayed edges, missing cog material, oil contamination or excessive stretching. Squealing, slipping, repeated loss of tension or a belt riding unusually low in the pulley groove can also indicate belt wear, pulley wear or incorrect fitment.
Installation Notes
Inspect all pulleys for corrosion, contamination, wear and misalignment before installing the replacement belt. Do not force the belt over the pulley flanges. Set the tension according to the engine manufacturer's specification, rotate the drive by hand to confirm correct seating and recheck the tension after the initial operating period.
Alternate / Superseded Part Numbers
- Sierra part number: 18-15550
- Supplier or catalogue reference: 47-15550
- Mallory: 9-55000
- Mercury MerCruiser: 57-13458
- Mercury Quicksilver: 57-13458Q
- Mercury MerCruiser: 57-13458T
- UPC: 030999566744
Parts Desk Insights
Best use case: This belt is the right choice for pre-season service and routine maintenance on MerCruiser 7.4L/454 big-block inboard and sterndrive boats, particularly 330 GM 454 (1982–1987), 454 MAG Alpha (1986–1989) and 454 MAG Bravo/7.4L Bravo installations through the early 1990s. If your engine specifies OEM belt numbers 57-13458, 57-13458Q or 57-13458T, this is the direct replacement to have ready before launch. It also makes a practical onboard spare — a belt failure on a big-block can simultaneously take out raw water cooling, power steering and battery charging.
This belt is closely tied to the accessory and power-steering layout used on older MerCruiser big-block engines. Match the original belt number and pulley arrangement rather than ordering by engine displacement alone. Always verify the OEM belt number, drive model and production year before ordering.
For a complete cooling system service, pair this belt with a raw water pump impeller replacement. See the PCM Impeller Kit RP061017 and PCM / Crusader RP061022 Raw Water Pump Impeller for compatible options. Need a different belt size? Browse the Sierra V-Belt 47-15400, Sierra V-Belt 47-15410, Sierra V-Belt 47-15440, Sierra V-Belt 47-15450, Sierra V-Belt 47-15455, Sierra V-Belt 47-15460, Sierra V-Belt 47-15470, Sierra V-Belt 47-15480, and Sierra V-Belt 47-15520 for other sizes in the same series.
Shop all Engine Parts & Maintenance or browse Propulsion & Powertrain for related components.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.