Mercury / Quicksilver 807988A03 Cast-Iron Exhaust Elbow Assembly | MerCruiser 4.3L / 5.0L / 5.7L | 4 in. 7° Center-Rise

Part Details

• Part Number: 807988A03
• Brand: Mercury Marine / Quicksilver (Genuine OEM)
• Official Product Type: Cast-Iron Exhaust Elbow Assembly — Center-Rise
• Outlet Diameter: 4 in. / 102 mm outside diameter
• Outlet Angle: 7° downward
• Construction: Cast iron, hot-dipped and black top-coated
• System: Wet-joint center-rise exhaust system
• Includes: 2 brass 3/4-14 pipe fittings and 2 plugs
• Gasket: Sold separately — see Exhaust Elbow Gasket 863726
• Supersedes: 807988A2
• Typical Application Range: Through approximately model year 2002
• GTIN / UPC: 745061289055
• Weight (approx.): 4.5 kg / 10 lb (cast-iron elbow)

What This Part Is

Mercury / Quicksilver 807988A03 is a genuine OEM cast-iron exhaust elbow assembly for selected GM-based MerCruiser V6 and V8 sterndrive and inboard engines equipped with a center-rise exhaust manifold. The elbow connects the exhaust manifold outlet to the exhaust hose, routing exhaust gases and cooling water away from the engine. The 4 in. / 102 mm OD outlet exits at a 7° downward angle and the casting is hot-dipped and top-coated for corrosion protection.

Important: 807988A03 is for the older wet-joint center-rise exhaust system. It is not compatible with later dry-joint MerCruiser exhaust configurations, which use different mating surfaces and gasket arrangements. The exhaust gasket is sold separately — order Exhaust Elbow Gasket 863726 at the same time.

Compatible Applications

Fitment must be confirmed by engine model, serial number, manifold type, outlet diameter, and cooling-system configuration. Documented GM-based MerCruiser applications include:

• MerCruiser 4.3L V6 — center-rise exhaust, sterndrive and inboard (through approx. 2002)
• MerCruiser 5.0L V8 — center-rise exhaust, sterndrive and inboard (through approx. 2002)
• MerCruiser 5.7L / 350 CID V8 — center-rise exhaust, sterndrive and inboard (through approx. 2002)
• Other GM-based MerCruiser V6/V8 engines using the same center-rise 4 in. wet-joint exhaust configuration

Always verify 807988A03 in the exhaust manifold / elbow parts diagram for the specific engine serial number before ordering.

Kit Contents

• Cast-iron exhaust elbow assembly (807988A03)
• 2 × brass 3/4-14 pipe fittings
• 2 × plugs
• Gasket not included — order separately: Exhaust Elbow Gasket 863726

When to Replace

Replace the exhaust elbow if inspection shows any of the following:

• Internal corrosion, scaling, or restricted cooling-water passages
• External rust-through or holes in the casting
• Cracks in the casting (visible or detected by pressure test)
• Exhaust gas or water leakage at the elbow-to-manifold joint
• Severe pitting or deterioration at the gasket sealing surface
• Evidence of water intrusion toward the exhaust manifold or engine cylinders

Marine cast-iron exhaust elbows can corrode internally while appearing acceptable from the outside. Internal condition should be checked during any manifold service — a restricted or corroded elbow can allow water to back up toward the engine.

Service Interval

Mercury recommends inspecting exhaust elbows at regular engine service intervals. MerCruiser service guidelines generally call for exhaust system inspection every 2 years or 200 hours (whichever comes first) on saltwater-operated engines, and at least every 3 to 4 years on freshwater engines. Internal corrosion can progress rapidly in saltwater environments — do not defer inspection if the elbow has been in service for several seasons without being removed.

Installation Notes

• Always install a new exhaust elbow gasket (863726 or 8637251 depending on cooling configuration) — do not reuse the old gasket
• Inspect the mating exhaust manifold outlet flange for corrosion, warping, or damage before installing the new elbow
• Clean both sealing surfaces of all old gasket material
• Inspect the connected exhaust hose for heat cracking, softening, or deterioration and replace if needed
• Check the included brass fittings and surrounding cooling-water hoses for condition
• Verify the correct 4 in. exhaust-hose connection at the elbow outlet
• Tighten elbow fasteners evenly to the torque specified in the MerCruiser service procedure for the applicable engine
• After startup, check for exhaust gas or water leakage at the elbow joint and at the hose connection

Technical FAQ

How do I know if my engine uses a center-rise or dry-joint exhaust system?
Center-rise (wet-joint) exhaust systems route cooling water through the exhaust elbow alongside exhaust gases. The elbow has water inlet fittings and a wet joint to the manifold. Dry-joint systems use a riser that separates water injection from the manifold connection. The easiest confirmation is to check the MerCruiser parts diagram for your engine serial number and look for the elbow part number. If 807988A03 appears in the diagram, the center-rise system is installed.

Is the gasket included?
No. The exhaust elbow gasket is sold separately. Order Exhaust Elbow Gasket 863726 alongside the elbow — a new gasket should always be installed when the elbow is removed.

What supersedes 807988A2?
807988A03 is the direct replacement for 807988A2. Always use 807988A03 when ordering; 807988A2 is no longer the current production number.

Can I use this elbow on a later MerCruiser with a dry-joint exhaust?
No. The center-rise wet-joint elbow and the later dry-joint riser/elbow designs use different mating surfaces, gasket arrangements, and cooling-water routing. Installing the wrong type will result in leaks and potentially serious engine damage.

What aftermarket parts cross-reference to 807988A03?
Documented aftermarket equivalents include Sierra 18-1976-1 and 18-1976-2, GLM 51140, Mallory 9-40559, Osco 4354, and Barr MC-20-44354. Always verify the cross-reference against the OEM diagram for your specific engine before substituting.

Superseded / Cross-Reference Part Numbers

• Current Mercury OEM: 807988A03
• Superseded: 807988A2
• Sierra aftermarket: 18-1976-1, 18-1976-2
• GLM aftermarket: 51140
• Mallory aftermarket: 9-40559
• Osco aftermarket: 4354
• Barr aftermarket: MC-20-44354
• GTIN / UPC: 745061289055

Related Parts

• Mercury Quicksilver Exhaust Elbow Gasket 863726 — required; sold separately; order with elbow
• Browse MerCruiser Marine Engine Parts for all exhaust system components

Parts Desk Insights

Best use case: 807988A03 is the correct replacement elbow for older GM-based MerCruiser V6 and V8 engines (typically through approximately 2002) using the center-rise wet-joint exhaust system. It is most commonly ordered during scheduled exhaust system inspection, after a failed pressure test, or when water backing up into the manifold or cylinders has been traced to a corroded or cracked elbow.

Common issues: The most important fitment check is confirming the engine uses the center-rise wet-joint exhaust system — not the later dry-joint design. These two systems are not interchangeable, and ordering by engine family alone without verifying the exhaust type is the most frequent cause of a return. The second common issue is ordering the elbow without the gasket (863726) and having to wait for a second delivery before the job can be completed. Order both together.