OMC 4-Stroke 5.8L Marine Engine Parts

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This page is for OMC 4‑Stroke 5.8L marine engines (commonly found in Cobra sterndrive and inboard installations). Use it to find compatible parts and service information. Below you’ll find maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main OMC/Johnson/Evinrude collection for a wider selection. Scroll to the bottom of this page to start browsing parts for this engine, and on the collection page use the Filter & Sort controls to narrow results by horsepower/displacement, year range, and part category.

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How to Identify Your 5.8L Model

Nameplate location: Look for an ID tag on the intake manifold or valve cover; many OMC installations also include a sticker on the transom bracket or engine cover. Block stampings may be on a pad near the starboard/front of the engine.
Reading the code: Confirm “5.8L/351 CID,” carbureted vs EFI, and distributor supplier (often Prestolite). Suffixes can indicate model year or hardware variations.
Carb vs EFI: Carbureted 5.8L models use a mechanical fuel pump and marine carb; EFI models use an ECU, different ignition module, and matching cap/rotor.
Distributor hardware: Some Prestolite distributors use a spring-clip cap while others use a screw-retained cap; caps/rotors are not interchangeable, so verify before ordering.

Platform Overview

5.8L Carbureted (Ford 351 CID V8)

Feature	Description
Configuration	Naturally aspirated OHV V8, 4‑stroke, marine carburetor, conventional distributor ignition
Common Models	OMC Cobra 5.8L installations in the early 1990s; inboard variants also seen
Advantages	Strong low‑to‑mid torque, straightforward service, broad parts availability
Notes	Ignition tune‑up parts vary by distributor (spring‑clip vs screw‑retained). Verify cap/rotor style before ordering.

5.8L EFI (Ford 351 CID V8)

Feature	Description
Configuration	OHV V8, 4‑stroke, multi‑point or throttle‑body EFI (varies by build), ECU‑controlled ignition module
Common Models	OMC Cobra 5.8L EFI packages around the 1993–1994 timeframe
Advantages	Improved cold start and drivability, potentially better fuel economy vs carb
Notes	EFI models use different ignition modules and occasionally a different distributor cap/rotor set. Always match by model year and distributor hardware.

Routine Maintenance & Service Parts

Intervals below are general guidelines for typical recreational use. Always follow the official service manual for your exact model and duty cycle.

Item	Interval*	Remarks	Parts Link
Engine oil + filter	Every 100 hours or annually	Use marine‑rated oil; warm engine before draining for best results	Oil Filters
Gear oil (lower unit)	Every 100 hours or annually	Inspect magnetic drain plug; replace seals if water intrusion is found	Johnson/Evinrude/OMC Service Kits
Spark plugs	Inspect every 100 hours; replace 200–300 hours or as needed	Check gap and condition; fouling indicates mixture or ignition issues	Spark Plugs
Fuel filter / water separator	Every season or 100 hours	Replace more often with ethanol fuel or contaminated tanks	Fuel Filters
Raw‑water pump impeller/kit	Every 2 seasons (or 1 season in sandy/silty water)	Critical for cooling; replace sooner if overheat/weak stream occurs	Water Pumps
Anodes (zinc/aluminum/magnesium)	Inspect every 50 hours; replace when 50% depleted	Match material to water type (salt/brackish/fresh)	Johnson/Evinrude/OMC Anodes
Thermostat	Every 2–3 seasons	Replace if running cold or unstable temperature control	OMC Parts (General)
Alternator/serpentine belt	Inspect each service; replace if cracked or glazed	Proper belt tension protects alternator and water pump bearings	Belts
Ignition tune‑up (cap/rotor/wires)	Inspect annually; replace as needed	Match to distributor style (clip vs screw) and EFI vs carb model	Electrical Items

Frequently Used Parts Categories

Routine Service — Johnson/Evinrude/OMC Service & Maintenance Kits
Cooling System — Water Pumps
Fuel System — Fuel Filters
Ignition / Electrical — Electrical Items
Corrosion Protection — Johnson/Evinrude/OMC Anodes
Gearcase & Seals — Lower Unit Seal Kits
Propulsion — Propellers

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Overheat alarm or weak discharge	Inspect intake screens, sea strainer, and raw‑water pump; verify thermostat operation	Water pump kit, thermostat, intake screen, hoses
Hard starting / rough idle	Check fuel quality, filter/water separator, vacuum leaks; inspect spark plugs and ignition leads	Spark plugs, plug wires, distributor cap/rotor, fuel filter
Poor acceleration or power loss	Confirm prop condition/pitch; check timing/advance, fuel delivery, and for restricted exhaust	Propeller, fuel pump, filters, ignition module
Low charging voltage	Inspect belt tension, alternator output, and battery condition/connections	Belt, alternator, battery cables
Gearcase noise or metal in oil	Drain and inspect gear oil; check prop shaft for fishing line; pressure/vacuum test for seal leaks	Lower unit seals, bearings, gear oil

FAQs

Are ignition and tune‑up parts interchangeable across all 5.8L years?

No. OMC used different distributor hardware (spring‑clip vs screw‑retained caps) and EFI versions may use different modules and caps. Match by model year, carb vs EFI, and distributor style.

When should I replace the raw‑water pump impeller?

Every two seasons is typical for recreational use. Replace sooner (every season) if operated in sandy/silty water or if any overheat/weak stream symptoms occur.

How often should lower unit gear oil be changed?

Change every 100 hours or annually, and always after any known water intrusion or prop‑strike event. Inspect the magnetic drain plug for metal debris.

What information do you need to confirm part compatibility?

Please provide the engine model/serial, carb vs EFI, distributor style (clip or screw cap), and the drive model. Photos of the nameplate and the existing part help ensure a correct match.

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If you’re unsure about your model, send us a clear photo of the nameplate and the part you need and we’ll help verify compatibility.