Mercury 2-Stroke 9.8HP Outboard Engine Parts

(16 products)

Parts and maintenance guide for Mercury 2-Stroke 9.8HP outboard engines. Use this page to find compatible parts, routine service information, maintenance tips, common replacement items, and troubleshooting guidance. You can also browse the main Mercury collection. Scroll to the bottom of the page to start browsing parts for this engine, and 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 9.8HP Model

Find the serial/nameplate: typically stamped on the transom clamp bracket or swivel bracket. This serial is the key reference for accurate parts lookup.
Understand suffixes and options: short shaft (often “S” ~15) vs long shaft (often “L” ~20) affect driveshaft housing and water tube/impeller stack. Note control type (tiller vs. remote) and starting (manual vs. electric).
2-Stroke identifiers: requires premix or an oil-injection system; visible choke and carburetor. Some 9.8HP models use either Tillotson or Walbro (WMB series) carb variants across serial ranges.
Record what you see: carb stamp (if visible), shaft length, and serial number. These details help verify water pump kits, carburetor service parts, and ignition items.

Engine Overview

Mercury 9.8HP 2 -Stroke Twin (Carbureted)

Feature	Description
Configuration	Inline 2-cylinder, carbureted 2-stroke outboard; manual choke; lightweight portable class.
Common Models	Mercury 9.8HP 2-Stroke in short- and long-shaft versions; tiller or remote control; manual or electric start depending on serial range.
Advantages	Simple service, strong low-mid torque, and very good portability for small boats and tenders.
Notes	Carburetor supplier varies by serial (e.g., Tillotson vs. Walbro WMB). Some cooling and gearcase parts differ by shaft length and serial breaksverify with your serial number.

Routine Maintenance & Service Parts

Intervals below are typical guidelines for small 2-strokes; always follow your engines official service manual and maintenance schedule.

Item	Interval*	Remarks	Parts Link
Gear oil (lower unit)	Every 100 hours or annually	Check for water (milky oil). Replace sealing washers; reseal if intrusion is found.	Mercury Lower Unit Seal Kits
Spark plugs	Inspect each season; replace ~100 hours	Use the correct heat range and gap; fouled plugs cause hard starting and poor idle.	Spark Plugs
Fuel filter (inline)	Every 100 hours or annually	Replace and inspect for debris or water. Check hose condition at the same time.	Fuel Filters
Water pump impeller / kit	100 hours or 2 seasons (annually in sandy/silty water)	Weak tell-tale or overheat warnings often indicate impeller wear. Verify kit by serial and shaft length.	Mercury Water Pump Repair Kits
Anodes (zincs)	Inspect often; replace when ~50% depleted	Choose material for your water (zinc/salt, aluminum/brackish, magnesium/fresh). Maintain clean, tight contact.	Anodes
Fuel line & quick connector	Every 2 years or at first sign of cracks/leaks	Ethanol can harden hoses. Replace primer bulb if it wont firm up or cracks.	Fuel Line & Connector
2-Stroke fuel/oil mix	Every fill-up	Mix gasoline with TC-W3 marine 2-stroke oil per the service manual (many run 50:1). Use fresh fuel.	Mercury Outboard Parts

Frequently Used Parts Categories

Cooling System Mercury Water Pump Repair Kits
Fuel System Fuel Filters
Ignition / Electrical Electrical Items
Gearcase & Seals Mercury Lower Unit Seal Kits
Carburetor & Induction Carburetor
Propulsion Propellers
Safety Add-ons Propeller Guards

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak tell-tale or overheat alarm	Inspect intake screen for blockage; test impeller output; verify thermostat function; confirm water tube alignment on reassembly.	Water pump kit, intake screen, thermostat, gaskets
Hard starting / rough idle	Confirm choke operation; prime bulb should get firm; check for air leaks at tank quick-connector; inspect idle mixture and carb cleanliness.	Carburetor repair kit, fuel connector/lines, spark plugs
Poor acceleration / power loss	Check propeller for damage or over-pitching; replace clogged fuel filter; verify full throttle opening and timing per manual.	Propeller, fuel filter, carb kit, spark plugs
Excessive smoke (2-Stroke)	Confirm premix ratio; ensure choke is not stuck closed; look for rich idle mixture settings.	Spark plugs, carburetor repair kit
Gearcase noise / metal in oil	Drain and inspect gear oil; check for water intrusion at seals; verify prop shaft is straight and hardware torqued.	Lower unit seal kit, bearings, prop shaft hardware

FAQs

Are parts interchangeable between different years or carb suppliers?

Many service items interchange across serial ranges, but some components differ by serial number and carburetor supplier (e.g., Tillotson vs. Walbro). Always confirm using your engines serial and visible carb stamp when applicable.

When should the water pump impeller be replaced?

As a preventative measure every 100 hours or 2 seasons, and annually if you operate in silty/sandy water or notice a weak tell-tale stream. Replace sooner after any overheat event.

How often should I change lower unit gear oil?

Change gear oil every 100 hours or at least once per season. If oil appears milky, reseal the gearcase and retest to prevent bearing and gear damage.

What information helps confirm part compatibility?

Provide the engine serial number, shaft length (S/L), starting type (manual/electric), control type (tiller/remote), and any carburetor stamps. Photos of the nameplate and the part being replaced are very helpful.

Ready to find the parts you need? Browse the Mercury collection and filter by horsepower, model, and category to zero in on components for your 9.8HP 2-Stroke.

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If youre unsure about your model, send us a photo of the nameplate and the part you need and well help verify compatibility.