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 circuit — not a generic protective cap or plug. The cap is secured by a worm-gear clamp and typically appears once per manifold, meaning two per engine. 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 configurations within the same engine family. Confirm fitment by engine serial number and the applicable exhaust manifold diagram rather than by displacement alone.

• 5.7L / 350 CID V8 — Selected sterndrive and inboard exhaust manifold assemblies where the diagram specifies 805727001
• 7.4L / 454 CID V8 — Selected 7.4L MIE and big-block exhaust manifold assemblies
• 8.2L / 502 CID V8 — Selected 454 Magnum and 502 Magnum big-block applications

When This Part Needs Replacement

• The rubber is cracked, hardened, or swollen from heat exposure
• Cooling water is leaking around the cap area
• The cap no longer seats tightly in its manifold connection
• The retaining clamp is corroded or unable to hold the cap securely
• Exhaust manifold service requires removal of the cap
• The original cap was visibly deteriorated during disassembly

A heat-aged 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 — Exhaust gasket (search by part number)
• 862210A01 — Drain elbow kit (search by part number)
• 8M0119211 — Drain plug kit (search by part number)
• 32509 — Quad ring (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 fitting where the cap seats before installing
• Replace a corroded or distorted retaining clamp (815504220) at the same time
• Push the cap fully into position before tightening the clamp
• Check the opposite-side cap while exhaust access is open
• Inspect for cooling leaks after reassembly
• Follow the applicable MerCruiser service procedure for the specific exhaust manifold configuration

Parts Desk Insights

Most common customer issue: Ordering a single cap when two are needed. This cap is part of the exhaust manifold cooling hardware and is installed in pairs on applicable V8 engines — one per manifold, two per engine. If you're replacing due to a leak, order both caps and replace both clamps (815504220) at the same time.

Best use case: Ideal for customers doing a full exhaust manifold service, addressing a cooling water weep at the manifold cap, or refreshing high-hour exhaust hardware before the boating season. A low-cost part that's easy to overlook and commonly causes post-service leaks if the old one is reused.