86840A05 U-Joint Bellow Fits MerCruiser Bravo I, II, III and Blackhawk sterndrives

86840A05 U-Joint Bellow — Fits MerCruiser Bravo I, II, III and Blackhawk sterndrives, Replaces 18-2756, 89140, 64840P, 8M0062406

GHMarine U-joint bellow (universal joint grease boot) for the drive shaft inside the bell housing on compatible MerCruiser Bravo I, II, III and Blackhawk sterndrives. Replaces OEM 86840A05 and cross-ref 18-2756, 89140, 64840P, 8M0062406. Match your drive serial in the table below.

Ships as one Bravo U-joint bellow — not the full transom service kit. Two hose clamps on the boot when shown; sleeve and grounding clip when shown in photos. Marine bellows adhesive and expander tool (ref 91-45497A1) sold separately.

Which bellow is this?

This is the largest U-joint / drive-shaft accordion boot inside the bell housing — it wraps the universal joint. It is not the exhaust bellow at the transom, the shift cable bellow, the raw-water hose, or a gimbal bearing kit.

Kit photos may show all transom parts together; this SKU is the drive U-joint boot only (86840A05 family).

What to inspect with the drive off

·       Water in the U-joint cavity after running — the Bravo drive bellow is the water seal around the universal joint inside the bell housing. Cracks, pinholes, or soft accordion ribs let salt water reach U-joints and the gimbal area.

·       Every time the sterndrive comes off for service — inspect the large accordion boot for splits, UV checking, or hardened rubber. On Bravo drives the boot sees heavy trim and steering movement; replace on sight, not after the season.

·       Grease weeping or rusty U-joint caps under a torn boot — the boot keeps grease in and water out. Re-greasing the joint will not fix a compromised seal.

·       Clunk, vibration, or rough trim/steering feel — a collapsed or torn boot often shows up as drivetrain noise before you see bilge water. Catch rubber failure at inspection, not on the first hard launch of the year.

·       Loose or corroded hose clamps at either end — Bravo U-joint boots typically use two stainless clamps. Rusty, stretched, or missing clamps mean the boot is not sealed even if the rubber still looks okay.

·       Do not confuse with other transom wetness — exhaust leaks (GHMarine 17B1003) or shift-cable seepage (17B1005) are different locations. This boot wraps the drive shaft universal joint inside the bell housing (86840A05).

Will it fit my drive?

This U-joint bellow is Compatible with MerCruiser Bravo I (1988+), Bravo II (1991+), Bravo III (1994+), and Blackhawk (1994–1995) sterndrives that use OEM 86840A05. NOT Alpha One Gen I — see GHMarine 17B1004. NOT Alpha Gen II / Vazer — see GHMarine 17B1007. Confirm drive serial before you order.

Brand	Model / Drive	Rated HP	Stroke	Years	OEM Part No.
MerCruiser	Bravo One (Bravo I)	260–350	Sterndrive	1988–Current	86840A05
MerCruiser	Bravo Two (Bravo II)	260–380	Sterndrive	1991–Current	86840A05
MerCruiser	Bravo Three (Bravo III)	300–430	Sterndrive	1994–Current	86840A05
MerCruiser	Blackhawk	300–430	Sterndrive	1994–1995	86840A05

 

OEM & swap numbers

Primary OEM is 86840A05 (supersede family 8M0062406). Common interchange refs: 18-2756, 89140, 64840P.

Type	Part Number	Notes
OEM	86840A05	Bravo U-joint bellow / universal joint grease boot
OEM supersede	8M0062406	Current Quicksilver catalog family — same Bravo U-joint boot
Cross-ref	18-2756	Sierra — Bravo I/II/III U-joint bellows
Cross-ref	89140	GLM — Bravo U-joint bellow
Cross-ref	64840P	PROmarine — w/Sleeve 1988-Up
Cross-ref	REC86840A05	Recmar catalog ID

 

Wrong part? Read before you order

·       NOT for Alpha One Gen II / Vazer (816431A1) — different drive boot; see GHMarine 17B1007.

·       NOT for Alpha One Gen I (60932A4) — see GHMarine 17B1004.

·       NOT for bell-housing exhaust bellow 8M0124227 / 18654A1 — that is GHMarine 17B1003.

·       NOT for shift cable bellow 74639A2 — that is GHMarine 17B1005.

·       NOT for Bravo transom service kit (three bellows + hose + bearing) — see GHMarine 17B3003; this listing is the U-joint boot only.

What ships in the box

·       1 × Bravo U-joint bellow (86840A05 family) — single drive boot, not full transom kit

·       2 × stainless hose clamps on the boot when shown in product photos

·       Metal sleeve and grounding clip when shown in product photos

·       Not included: bellows adhesive, expander tool 91-45497A1 (unless shown)

Often ordered with the other transom boots

·       Exhaust bellow (bell housing) — GH SKU 17B1003 (ref 8M0124227 family).

·       Shift cable bellow — GH SKU 17B1005 (ref 74639A2).

·       Bravo three-bellow kit — GH SKU 17B3003 if you need drive + exhaust + shift together.

·       Alpha Gen II U-joint — GH SKU 17B1007 (ref 816431A1) — different drive, not this listing.

·       Alpha Gen I U-joint — GH SKU 17B1004 (ref 60932A4).

·       Many shops install shift and U-joint boots first; put the exhaust bellow on last — it is the tightest fit.

Install tips while the drive is off

Remove the sterndrive per your service manual. Work in a ventilated area. Professional install recommended if you are not comfortable with drive removal.

1. Inspect U-joints, gimbal bearing, and input shaft before installing new rubber.

2. Remove old boot; clean bell housing flange and drive shaft landing areas.

3. Apply marine bellows adhesive to both boot ends; let dry until not tacky (often 10–20 minutes).

4. Install large end on bell housing first; tighten both clamps through access holes.

5. Use bellows expander tool (OEM ref 91-45497A1) on the drive-shaft end; tighten clamps securely.

6. Reinstall grounding clip if supplied; reinstall drive; run on muffs; check for water intrusion at the U-joint cavity after a heat cycle.

FAQ

Will this fit my Alpha One or Bravo?

U-joint bellow for MerCruiser Bravo I, II, III and Blackhawk only (86840A05). NOT Alpha Gen I (see GHMarine 17B1004). NOT Alpha Gen II / Vazer (see GHMarine 17B1007). Match drive serial on the sterndrive tag — horsepower alone is not enough.

What is in the box?

One Bravo U-joint bellow (86840A05 family) — not the full transom kit. Product photos show two stainless hose clamps on the boot; sleeve and grounding clip when shown. Marine bellows adhesive and expander tool 91-45497A1 sold separately unless shown.

How is this different from the exhaust or shift bellow?

This is the largest accordion boot on the drive shaft universal joint (86840A05). Exhaust bellow = 8M0124227 (GH SKU 17B1003). Shift cable bellow = 74639A2 (GH SKU 17B1005). Three different locations, three SKUs.

Is this the same as the three-bellow kit?

No. GHMarine 17B3003 is the Bravo three-bellow kit (drive + exhaust + shift). This listing 17B1006 is the drive U-joint boot only — the large accordion bellow in the center of kit photos.

Please note

Aftermarket replacement part. Not affiliated with engine manufacturers named above. "Compatible with", "Replaces", and cross-ref numbers mean this part is built to work like the originals listed — always confirm fit with your drive serial number.