86840A05 U-Joint Bellow for Mercruiser Bravo I II III Blackhawk | JLM Marine

U-Joint Bellow for Mercruiser Bravo I II III Blackhawk – OEM 86840A05 Replacement

This U-Joint bellow is designed as a direct replacement for Mercruiser Bravo I, II, III, and Blackhawk sterndrive models from 1988 and up. Engineered to protect the universal joint from water intrusion and contamination, this bellow ensures reliable performance and extends the service life of your engine bell housing assembly.

Replaces OEM part numbers 86840A3, 86840A05, and 8M0062406, as well as aftermarket equivalents including Sierra 18-2756 and Mallory 89140. This kit includes all necessary installation components for a complete repair.

• Complete kit with bellow, clamps, clips, and sleeve
• Features bellow with ridge for improved durability
• Fits Mercruiser Bravo and Blackhawk sterndrive systems

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 complete kit includes:

• 1 × U-Joint Bellow (with ridge)
• 1 × Clamps
• 1 × Clips
• 1 × Sleeve

Installation Guide

1. Preparation: Disconnect the battery and raise the sterndrive to access the gimbal housing area. Remove the drive unit according to your service manual.
2. Remove Old Bellow: Cut off the old U-joint bellow and remove the retaining clamps and clips from the gimbal housing and bell housing.
3. Clean Surfaces: Thoroughly clean the bell housing and gimbal housing surfaces where the new bellow will seat. Remove all debris, corrosion, and old adhesive.
4. Install Sleeve: Slide the provided sleeve onto the U-joint shaft at the correct position as indicated in your service manual.
5. Position New Bellow: Carefully slide the new U-joint bellow over the shaft and align it with the bell housing groove, ensuring the ridge faces the correct direction.
6. Secure with Clamps: Install the provided clamps at both ends of the bellow and tighten evenly to the recommended torque specification. Attach clips to secure the bellow in place.
7. Inspect Installation: Verify that the bellow is seated properly without twists or kinks and that all clamps are secure.
8. Reassemble Drive: Reinstall the sterndrive unit following your service manual procedures. Reconnect the battery and test for leaks by running the engine in a test tank or on the water.

Troubleshooting & FAQ

Q: How do I confirm this U-joint bellow fits my Mercruiser engine?
A: Check the compatibility table above for your model and year, then verify your serial number falls within the specified range (0B664190 & Up for Bravo models, 0F186717 & Up for Blackhawk). Cross-reference your current bellow's OEM number with the part numbers listed.

Q: How often should I replace the U-joint bellow?
A: Inspect the U-joint bellow annually or every 100 hours of operation for cracks, tears, or deterioration. Replace immediately if you notice any damage, as a failed bellow can allow water into the gimbal bearing and cause serious damage.

Q: What are the signs that my U-joint bellow is failing?
A: Common symptoms include visible cracks or splits in the rubber, water in the bilge near the transom assembly, corrosion on the U-joint or gimbal bearing, and excessive play or noise during engine operation.

Q: Does this kit include all the parts I need for installation?
A: Yes, this kit includes the U-joint bellow with ridge, clamps, clips, and sleeve—everything needed for a complete installation. You may want to apply marine grease to the U-joint during reassembly (sold separately).

Q: What's the difference between OEM and aftermarket U-joint bellows?
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.

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.