MerCruiser Exhaust Manifold Rubber Cap 805727001

Exhaust Manifold Rubber Cap — Part 805727001

This is the genuine OEM rubber cap used in MerCruiser exhaust manifold and exhaust elbow assemblies on selected V8 engines. It is part of the exhaust manifold cooling hardware — not a generic protective cap. The cap is retained by a worm-gear clamp and typically appears twice on applicable engines, once per side. If one cap shows heat damage or leakage, inspect the opposite-side cap and its clamp at the same time.

Supersedes / Part Number Reference

• Current OEM number: 805727001 / 19-805727001
• Supersedes: 805727 / 19-805727

Compatible Applications

MerCruiser used several exhaust manifold, riser, and cooling arrangements within the same engine family. Confirm fitment by engine serial number and the applicable exhaust manifold diagram.

• 5.7L / 350 CID V8 — 5.7L Alpha EFI TBI, 5.7L Bravo EFI TBI, and other 5.7L applications using the same capped manifold arrangement
• 7.4L / 454 CID V8 — 7.4L MIE Gen V, 7.4L MIE MPI Gen V, 7.4L TBI MIE Gen VI, and additional 7.4L / 454 exhaust manifold assemblies
• 454 Magnum / 8.2L / 502 CID V8 — Selected 454 Magnum and 502 Magnum big-block applications where the exhaust manifold diagram specifies 805727001

When This Part Needs Replacement

• The rubber is cracked, hardened, or distorted from heat exposure
• Coolant or raw water is leaking around the cap
• The cap has swollen and can no longer seat correctly
• The retaining clamp can no longer secure it properly
• The exhaust manifold is being replaced or serviced
• The original cap was damaged during disassembly

A heat-aged or deteriorated cap should not be reused during manifold service.

Related Parts

• 815504220 / 54-815504220 — Worm-gear clamp (retains this cap — search by part number)
• Mercury MerCruiser Quicksilver Exhaust Manifold Assembly 807078T10
• 816900A5 / 816900A9 — Exhaust elbow assemblies (search by part number)
• 863724 — Standard-cooling exhaust gasket (search by part number)
• 863726 — Exhaust gasket for riser-kit applications (search by part number)
• 862210A01 — Drain elbow kit (search by part number)
• 8M0119211 — Drain plug kit (search by part number)
• 93320A14 — 3-inch exhaust riser kit (search by part number)
• 807477A5 — 6-inch exhaust riser kit (search by part number)

Installation Notes

• Inspect the manifold connection surface before installing the new cap
• Replace a corroded or stretched retaining clamp (815504220) at the same time
• Seat the rubber cap fully before tightening the clamp
• Check the opposite-side cap while access is open — both typically wear at the same rate
• Pressure-test or inspect the cooling and exhaust system for leakage after service
• Follow the applicable MerCruiser service procedure for the exact manifold arrangement

Parts Desk Insights

Most common customer issue: Ordering a single cap when two are needed. Most applicable V8 engines use one cap per manifold — two total per engine. If you're replacing due to leakage or heat damage, order a pair and replace both clamps (815504220) at the same time to avoid a repeat job.

Best use case: Ideal for customers servicing or replacing MerCruiser V8 exhaust manifolds, addressing coolant weeps at the manifold cap area, or completing a full exhaust manifold refresh on high-hour engines. A low-cost component that's easy to miss during a manifold job and commonly the source of post-service leaks if reused.