Mercury FourStroke 75 / 80 / 90 / 100 / 115: manual and…

Specifications for Mercury FourStroke 75 / 80 / 90 / 100 / 115
Power	75–115 hp
Cylinders	4
Displacement	2,061 cm³ (2.1 l generation)
Fuel	Petrol
Type	Outboard

Autumn and spring plan for Mercury FourStroke 75 / 80 / 90 / 100 / 115

Here's what to do when hauling out and launching. Always follow the instruction book for your engine.

Autumn

Change the engine oil and oil filterevery 100 hours or annually
Change gear oilevery 100 hours or annually
Check the low-pressure fuel filterReplace as needed. · every 100 hours or annually
Grease the propeller shaftevery 100 hours or annually
Check the anodesevery 100 hours or annually
Flush the engine with fresh water
Run the carburettor dry or add fuel stabiliserFollow the manufacturer's instructions.
Lubricate according to the lubrication schedule

Spring

Check the thermostatPerformed by a Mercury workshop. · every 100 hours or annually
Replace the impellerPerformed by a Mercury workshop. · every 300 hours or every 36 months
Check the gearcase oilMilky oil means there is water in the gear housing.
Check the propeller and anodes
Check that cooling water comes out of the tell-tale hole

Add to calendar Tick off in the service bookTwo reminders a year: in April and in October.

Good to know

Tips

Replace the impeller every 300 hours or every three years

Mercury includes water pump impeller replacement in the 300-hour service, every 300 hours or every three years, and more often if the engine runs hot or water pressure drops.

Mercury 75/90/115 FourStroke owner's manual 2025 (external link) · page 97 (PDF-sida)

Same base engine

Applies to the power variants of Mercury FourStroke 75 / 80 / 90 / 100 / 115

75, 90 and 115 FourStroke share the same base engine

Mercury's owner's manual lists the same four-cylinder engine with 2 061 cm³ displacement for 75, 80, 90, 100 and 115 hp.

Differences according to the manufacturer

Full throttle range 4,500 to 5,500 rpm for 75 and 80 hp
Full throttle range 5,000 to 6,000 rpm for 90, 100 and 115 hp

Official power upgrade: No official upgrade found

Mercury 75/90/115 FourStroke owner's manual 2025 (external link) · page 27 (PDF-sida)

Law, safety and insurance

The boat must not have a more powerful engine than the maximum power specified by the boat manufacturer in the owner's manual or CE documentation. An overpowered engine can impair steering and buoyancy or damage the transom. Mercury operator's manual, boat power limit (external link)

Under the Recreational Craft Directive 2013/53/EU, increasing the rated power by more than 15 percent counts as a major engine modification, which requires a new conformity assessment before the engine is used. Directive 2013/53/EU, Articles 3 and 19 (external link)

If's boat insurance terms state that the boat must not have a more powerful engine than it is approved for, otherwise compensation may be reduced or denied. If boat insurance, terms section 3.3.4 (external link)

The warranty may be affected: Volvo Penta excludes faults caused by modified software or electronics, and Mercury warns that the warranty may be voided by improper use. Volvo Penta warranty terms, page 6 (external link) · Mercury operator's manual, warranty (external link)

Marinpedia does not publish instructions for unlocking power, as this can make the boat dangerous, violate CE regulations and affect insurance and warranty.

Troubleshooting

Starting problems

Runs rough, stalls or loses power

Smoke and exhaust

Oil, water and fuel

Electrics, alarms and fault codes

Drive, gearbox and trim

Outboard

Manuals

Official
Operation, maintenance and installation manual (external link)
EN · PDF · 2018
Official
Operation, maintenance and installation manual (2025) (external link)
EN · PDF · 2025

Spare parts

Spare parts for Mercury FourStroke 75 / 80 / 90 / 100 / 115
Part	Part number	Note	Source
100 h service kit (filters, seals)	8M00978541 pcsBuy (1)	75–115 hp 2.1L, serial no. 2B094996 and higher	MercruiserParts.com: Mercury 100/300-hour service kits (www.mercruiserparts.com)
100 h service kit (filters, seals)	8M00978561 pcsBuy (1)	75–115 hp 1.7L, serial no. 1B366823–2B094995	MercruiserParts.com: Mercury 100/300-hour service kits (www.mercruiserparts.com)
Service kit 300 h (water pump kit etc.)	8M00978551 pcsBuy (1)	75–115 hp 2.1L, serial no. 2B094996 and higher	MercruiserParts.com: Mercury 100/300-hour service kits (www.mercruiserparts.com)
Service kit 300 h (water pump kit etc.)	8M00978571 pcsBuy (1)	75–115 hp 1.7L, serial no. 1B366823–2B094995	MercruiserParts.com: Mercury 100/300-hour service kits (www.mercruiserparts.com)

Listings for Mercury FourStroke 75 / 80 / 90 / 100 / 115

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Service guides

Replacing the impeller →Winterize a boat engine →

Frequently asked questions about Mercury FourStroke 75 / 80 / 90 / 100 / 115

Where can I find the owner's manual for Mercury FourStroke 75 / 80 / 90 / 100 / 115?

Links to owner's manuals and workshop manuals are available under Manuals.

How many cylinders does Mercury FourStroke 75 / 80 / 90 / 100 / 115 have?

Mercury FourStroke 75 / 80 / 90 / 100 / 115 has 4 cylinders.

What fuel does the Mercury FourStroke 75 / 80 / 90 / 100 / 115 use?

Mercury FourStroke 75 / 80 / 90 / 100 / 115 runs on petrol.

Sources

Mercury Marine: Operation, Maintenance & Installation Manual (PDF) (external link)
Mercury Marine: Owner's Manual (search by serial number) (external link)
Mercury Marine: 2025 manual (PDF) (external link)
Wikipedia: Mercury Marine (en) (external link)
MercruiserParts.com: Mercury 100/300-hour service kits (www.mercruiserparts.com)

Mercury FourStroke 75 / 80 / 90 / 100 / 115

Engine data