70981A3 Exhaust Bellows for Mercruiser | JLM Marine

Exhaust Bellows for Mercruiser 3-4" – Replaces 70981A3

This upper exhaust bellows is designed for MerCruiser stern drive applications with 3-4 inch exhaust systems. It provides a flexible, durable seal between the exhaust manifold and transom assembly, engineered to meet or exceed OEM specifications for reliable performance in marine environments.

This bellows serves as a direct replacement for MerCruiser part number 70981A3, Sierra 18-2762, and Mallory 89070. It is compatible with a wide range of MerCruiser V6 and V8 engines from the early 1980s to present, including popular Chevy small-block and big-block configurations.

• Installs on 3-inch 15-degree center-mounted risers with 4-inch elbow
• Designed for 165/170/3.7L/180/190/470/485/488 manifolds and multiple V6/V8 engine families
• Exact-fit construction as pictured for straightforward installation

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below.

Technical Specifications

Package Contents

This package includes:

• 1 × Exhaust Bellows (3-4")

Installation Guide

1. Disconnect the battery and ensure the engine is cool before beginning work.
2. Remove the drive unit according to your MerCruiser service manual to access the exhaust bellows area.
3. Loosen and remove the hose clamps securing the old exhaust bellows to the manifold elbow and transom housing.
4. Carefully slide the worn bellows off the fittings, inspecting the mating surfaces for corrosion or damage.
5. Clean both the manifold elbow and transom connection points thoroughly; remove any old gasket material or carbon buildup.
6. Apply a thin layer of marine-grade silicone lubricant to the inside lips of the new bellows for easier installation.
7. Slide the new bellows onto the 3-inch riser elbow first, ensuring it seats fully without twisting.
8. Position the opposite end over the transom exhaust tube and align it squarely.
9. Install new stainless-steel hose clamps at both ends and tighten evenly to the torque specified in your service manual (typically 40–60 in-lbs).
10. Inspect the bellows for proper alignment and ensure there are no kinks or gaps that could cause exhaust leaks.
11. Reinstall the stern drive unit, reconnect the battery, and run the engine briefly to check for leaks or unusual exhaust noise.
12. Perform a final inspection after the first few hours of operation to confirm clamp tightness and seal integrity.

Troubleshooting & FAQ

Q: How do I confirm this bellows fits my MerCruiser stern drive?
A: Verify that your engine uses a 3-inch 15-degree center-mounted riser with a 4-inch elbow, and cross-reference your model year and engine size with the compatibility table above. If your original part number is 70981A3, 18-2762, or 89070, this bellows is a direct fit.

Q: How often should I replace my exhaust bellows?
A: Inspect your exhaust bellows annually for cracks, hardening, or carbon buildup. Most marine mechanics recommend replacement every 3–5 years or sooner if you notice exhaust odors, soot near the transom, or visible deterioration.

Q: What are the signs that my exhaust bellows is failing?
A: Common symptoms include exhaust fumes in the bilge, visible cracks or splits in the rubber, water intrusion near the transom assembly, or a hissing sound under load. Replace immediately if any of these occur to prevent engine damage or carbon monoxide hazards.

Q: Can I reuse my old hose clamps during installation?
A: It is strongly recommended to use new stainless-steel hose clamps. Old clamps may have reduced clamping force or corrosion, which can lead to exhaust leaks and premature bellows failure.

Q: Is this an OEM part or an aftermarket replacement?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.