70981A3 Upper Exhaust Boot 3" Riser to Elbow Tube Fits MerCruiser center rise V6/V8 sterndrive (Alpha / Bravo)

70981A3 Upper Exhaust Boot — 3" Riser to Elbow Tube

Fits MerCruiser center rise V6/V8 sterndrive (Alpha / Bravo) · Replaces 70981A3 · Also 53114A1, 18-2762, 9-72808, 89070

This is the 3" upper exhaust boot on a MerCruiser center-rise sterndrive — the rubber between the center riser and the 4" elbow in the engine bay. Parts books call it 70981A3; a lot of guys just say "upper exhaust tube." Read the number on the piece you pull off.

Also crosses to 53114A1, 18-2762, 9-72808, 89070.

Where does it go?

On a MerCruiser center-rise drive, this is the 3" bellow at the riser-to-elbow joint — in the engine bay, above the 4" elbow, before the transom plate. Open the hatch and trace exhaust from the manifold; you can usually reach it without pulling the drive.

Stamps are usually 70981A3 or 53114A1. Confirm 3" I.D. and that it sat above the elbow — not the 3" boot below (that is 32-90949T / GHMarine 24B1052). Wrong size or spot? Use Wrong boot? below.

Replace it if…

·       Raspy exhaust under the engine hatch at idle — crack or loose clamp at the 3" riser-to-elbow joint shows up as noise before you see water.

·       Black soot on the riser flange or elbow rubber — blow-by at this upper 3" section. Soot at the 4" riser-to-Y joint points to 17B1001 instead.

·       Bilge pump runs after a short trip — wet exhaust runs through this rubber in the engine bay. A split here dumps water inside, not just at the stern.

·       Exhaust smell when you lift the hatch — don't keep running it. Fix the leak before passengers sit downwind of the engine cover.

·       Hard, cracked, or burnt rubber after an overheat (no raw water, bad impeller) — replace even if it still looks attached. Quick check: leak below the elbow → 24B1052; measures 4" I.D. → 17B1002; water outside transom when parked → 17B1003.

Will it fit my drive?

HP on the engine tag won't tell you. Match the serial on the drive or transom and confirm 3" I.D. plus 70981A3 / 53114A1 on the old rubber.

Drive / setup	Years	What to check	Part #	Notes
MerCruiser center rise V6/V8	1971–present	3" upper at riser → 4" elbow; read serial tag	70981A3	Center-mounted riser family — not rear-mount Y-pipe only
MerCruiser Alpha center rise	1983–present	190–350 HP common; match stamped part #	70981A3	Engine-bay upper 3" — not 4" transom tube
MerCruiser 4.3 / 5.0 / 5.7L	1983–present	MCM center rise path	70981A3	Measure removed rubber — must read 3" I.D.
MerCruiser Bravo center rise	1988–present	Bravo SN 0B664190 & up	70981A3	Same 3" upper boot — confirm before order

 

Part numbers

OEM is 70981A3. 53114A1 is the elbow bellow on the same catalog drawing. Common swaps:

Type	Part Number	Notes
OEM	70981A3	Primary — upper 3 inch riser to 4 inch elbow
OEM	53114A1	Exhaust elbow bellow — same catalog drawing block
Cross-ref	18-2762	Interchange — replaces 70981 / 70981A3
Cross-ref	9-72808	Tube exhaust interchange
Cross-ref	9-72807	53114A1 adjacent catalog index
Cross-ref	89070	Upper 3 inch catalog numbering for 70981A3

 

Wrong boot? Check before you buy

3" upper vs 3" lower vs 4" everything — mix-ups happen every week. Need size + location + part #:

·       32-90949T / GHMarine 24B1052 — 3" boot below the elbow (lower wet exhaust).

·       32-44348T / GHMarine 17B1002 — 4" upper tube at the inner transom plate (both ends 4").

·       32-14358T / GHMarine 17B1001 — 4" riser elbow-to-Y boot farther upstream in the bay.

·       8M0124227 / GHMarine 17B1003 — big bell-housing boot outside the transom (drive-off job).

In the box

·       1 × upper 3" exhaust bellow (70981A3 family)

·       Hose clamps — if they're in the product photos

·       Not included: bellow adhesive, expander 91-45497A1, lower or transom boots

While you're in the engine bay…

Opening the riser/elbow area? Most shops eyeball the neighbors:

·       Lower 3" boot — GHMarine 24B1052 (32-90949T) below the elbow

·       4" riser boot — GHMarine 17B1001 (32-14358T) at elbow-to-Y

·       4" upper tube — GHMarine 17B1002 (32-44348T) at transom plate

·       Transom bell boot — GHMarine 17B1003 (8M0124227) if the drive is coming off anyway

Install (shop tips)

Let the exhaust cool. Usually no drive removal — work through the hatch. You may need to loosen the riser or manifold for room. This boot gets glued and clamped — not the soap-and-clamp-only trick on the 4" riser boot (17B1001).

Grab before you start

·       Marine bellows adhesive (3M Bellows Adhesive or same type — not RTV)

·       Expander tool 91-45497A1 on tight stubs

·       Hose clamps, wire brush, rags · good ventilation

Steps

1. Loosen both clamps. Remove the old upper boot; wire-brush the riser and elbow stubs.

2. Apply adhesive inside both ends of the new boot; wait until tacky (about 10–20 min).

3. Seat the boot on both flanges; use the expander if it's tight. Clamps in the grooves, even torque.

4. Reassemble anything you moved for access. Run at idle on muffs — sniff under the hatch and watch the bilge.

Questions

Upper 3 inch or lower 3 inch?

70981A3 is the upper piece — center riser to 4" elbow, above the bend. 32-90949T (24B1052) is the lower 3" boot below the elbow. Same nickname "exhaust boot," different spot — read the part number.

What's the deal with 70981A3 vs 53114A1?

Parts books show both on the same exhaust drawing. 70981A3 is the upper 3" tube/boot; 53114A1 is the elbow bellow on that path. Your old rubber may show either number — both are 3" upper family, not the 4" parts.

Do I have to pull the drive?

Usually no — this is an engine-bay job through the hatch. You may need to loosen the riser or manifold for clearance per your shop manual. That's different from the transom bell-housing boot (17B1003), where the drive often comes off.

Glue, clamps, or soap and water?

Most shops use marine bellows adhesive on both ends, then hose clamps in the grooves. Tight Gen II stubs — use expander 91-45497A1. Don't use RTV. The 4" riser boot (17B1001) is the clamp-and-lube job without adhesive — not this one.

How do I know 3 inch vs 4 inch?

Measure the inside diameter of what you removed. 70981A3 = 3" upper. 32-44348T = 4" upper at the transom plate. 32-14358T = 4" at the riser elbow. Part number beats guessing.

Should I change the lower boot too?

If you're already opening the elbow area, look at 32-90949T (24B1052) on the lower run — upper and lower 3" boots often age together.

What's in the box?

One upper 3" exhaust bellow (70981A3 family). Clamps if shown in the photos. No adhesive, no expander tool, no lower or transom boots.

Note

Aftermarket replacement. Not made by the engine maker. "Compatible with" and "Replaces" mean it fits like the OEM part — still match your serial tag and the number on the rubber you removed.