Johnson 20HP 2-Stroke Outboard Engine Parts

(39 products)

This page is dedicated to Johnson 2-Stroke 20 HP outboard engines. Use it to find compatible parts, routine service information, maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main Johnson/Evinrude collection, and at the bottom of this page you’ll find links to start browsing parts for this engine. On the collection page, use the “Filter & Sort” controls to narrow results by horsepower, year range, and part category/section.

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How to Identify Your 20 HP Model

Find the model/serial plate on the transom bracket or swivel bracket (often on the port side). The cowling decal alone is not enough to confirm parts.
Read the full model code: the base “20” indicates horsepower, while suffix letters typically denote shaft length, start type, and control style (e.g., short/long shaft, electric/manual start, tiller/remote). Year coding may also be embedded—verify against the plate.
Platform check: Johnson 20 HP two-strokes are generally inline 2‑cylinder, carbureted engines. Many use pre‑mix fuel; some later variants may have oil‑injection—confirm before ordering service items.
Measure shaft length (15" short vs 20" long) and note tiller vs remote control to ensure propeller, gearcase, and rigging parts match your setup.

Engine Overview

Johnson 20 HP 2‑Stroke (Inline‑2)

Feature	Description
Configuration	Inline‑2, carbureted, 2‑stroke, manual or electric start depending on model; water‑cooled with thermostatic control.
Common Models	Johnson 20 HP 2‑Stroke models (e.g., J20 series across late 1980s–1990s). Always confirm exact model/serial from the nameplate.
Advantages	Light weight, simple to service, reliable cooling pump design, strong low‑to‑mid‑range torque for small boats.
Notes	Many wear items (impeller, plugs, anodes) are widely shared, but ignition, carburetor jetting, and gear ratios can differ by year and sub‑model. Verify shaft length and starting/controls before ordering.

Routine Maintenance & Service Parts

Intervals below are general guidelines for Johnson 2‑Stroke 20 HP engines. Always follow the official service manual for your exact model and operating conditions.

Item	Interval*	Remarks	Parts Link
Gear Oil (Lower Unit)	Every 100 hours or annually	Change and inspect for water intrusion (milky oil) or metal shavings; replace drain plug gaskets as needed.	Johnson/Evinrude/OMC Lower Unit Seal Kits
Spark Plugs	Inspect 50 hours; replace 100 hours or annually	Use correct heat range and gap per your model’s manual; replace if fouled or worn.	Spark Plugs
Fuel Filter / Inline Filter	Every 100 hours or annually	Replace more often when dealing with stale/contaminated fuel. Consider adding a clear inline filter for quick checks.	Fuel Filters
Water Pump Impeller / Kit	Every 2–3 seasons (or 200 hours); annually in sandy/silty water	A weak tell‑tale or overheat alarm often indicates impeller wear or intake blockage.	Johnson/Evinrude/OMC Water Pump Repair Kits
Anodes (Sacrificial)	Inspect every 50 hours; replace when 50% consumed	Use alloy matched to your water type (fresh/brackish/salt). Keep contacts clean and tight.	Johnson/Evinrude/OMC Anodes
2‑Stroke Oil Supply (Pre‑mix or Oil Injection)	Check each fill‑up; inspect system pre‑season	Most 20 HP models use 50:1 (TC‑W3) pre‑mix; if equipped with oil injection, inspect hoses/pump and verify spec in the manual.	Johnson/Evinrude/OMC Hoses
Propeller & Hardware	Inspect each trip; service seasonally	Remove prop to check for fishing line, grease splines, and replace cotter pins as needed. Match pitch to your load.	Johnson/Evinrude/OMC Propellers

Frequently Used Parts Categories

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

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak tell‑tale or overheat alarm	Inspect intake screens for debris; verify strong water stream; check impeller condition and thermostat function.	Water pump kit, intake screen, thermostat, gaskets
Poor acceleration or loss of power	Check for stale fuel; replace/inspect fuel filter; confirm carburetor cleanliness and correct prop pitch.	Fuel filter, carburetor kit/cleaning parts, spark plugs, propeller
Hard starting / rough idle	Verify choke/primer operation; inspect spark plugs and plug wires; check for air leaks in fuel lines/bulb.	Spark plugs, fuel pump/lines, primer bulb, carburetor service parts
Excessive smoke (2‑stroke)	Confirm correct fuel/oil ratio; drain stale fuel; check for sticking choke/over‑rich idle mixture.	Spark plugs, carburetor cleaning kit, fuel lines
Gearcase noise or metal in gear oil	Check gear oil level/condition; look for water intrusion (milky oil); inspect prop shaft seals and bearings.	Lower unit seal kit, bearings, drain plug gaskets

FAQs

Are parts interchangeable between different years or platforms?

Many service items (impellers, plugs, anodes) carry across multiple years, but ignition components, carburetor parts, and gear ratios can vary. Always confirm the exact model and serial number from the nameplate before ordering.

When should I replace the impeller?

As a preventive measure, replace the impeller every 2–3 seasons (or ~200 hours). If you operate in sandy/silty or shallow waters, consider annual replacement. Weak tell‑tale, overheat alarms, or reduced flow at idle are signs to service sooner.

How often should I change the lower unit gear oil?

Change gear oil once per season or every 100 hours, whichever comes first. If the oil appears milky (water intrusion) or contains metal shavings, service the seals and inspect internal components before further use.

What information do you need to confirm part compatibility?

Please provide the model and serial number from the nameplate, shaft length (15"/20"), start type (manual/electric), and control type (tiller/remote). Photos of the nameplate and the part needing replacement are very helpful.

Ready to find parts by horsepower, year, and model? Browse the main Johnson/Evinrude collection to narrow down compatible components for your 20 HP two‑stroke.

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