Mercury Mercruiser Inboard Engine Care & Maintenance


Inboard and outboard engine maintenance share the important similarity of requiring regular maintenance to ensure long engine life and maximum fun out on the water. However, inbound engines are enclosed within the hull of the vessel, as opposed to outboard motors that are mounted outside the hull, and require some different maintenance steps.

Inboard Engine Components to Monitor & Maintain


Water Pump ImpellerMercury MerCruiser Alpha One Water Pump Impeller Repair Kit.jpg

Over time, the rubber impellers may dry, rust, and crack. A damaged water pump impeller can cause the engine to overheat and can cause very significant engine damage making it a problem that needs to be repaired immediately.

Most Popular Water Pump Repair Kits:

Mercury MerCruiser Alpha One Water Pump Impeller Repair Kit 817275Q05

Mercury MerCruiser Mariner Water Pump Impeller Repair Kit 47-8M0100526

Fuel-Water Separating Filter

Fuel-water separating filters are important to remove debris from your fuel than can clog and Mercury Fuel Water Seperating Filter with Wrench-1.jpgdamage your engine. Additionally, these filters are designed to remove excessive water from your fuel. PartsVu offers the filters as well as a fuel-water separating filter kit that includes the filter wrench.

Featured Products: 

Mercury Quicksilver Water Separating Fuel Filter

Mercury Quicksilver Water Separating Fuel Filter with Filter Wrench

*Stock Up and Save* – Mercury Quicksilver Water Separating Fuel Filter Multipacks

Propeller Shaft

The prop shaft should turn without any resistance. If the propeller shaft is turning stiffly, there could be problems with the shaft, engine mounts, strut, or engine alignment.


Anodes Mercury Bravo 3 Aluminum Anode Kit

Whenever you have two different metals immersed in saltwater, some amount of current flows between the two metals. The electrons that make up this current are supplied by one of the metals giving up bits of itself–in the form of metal ions–to the seawater. This is called galvanic corrosion and, left unchecked, it quickly destroys underwater metals. Anodes must be periodically replaced to prevent this damage.

Featured Product: 

Mercury MerCruiser Bravo 3 Aluminum Anode Kit 

Manifolds and Exhaust Riser

Check your inboard engine’s exhaust risers and manifolds for leaks as leaking exhaust risers can allow water to enter the engine.  Rust stains and corrosion on the exhaust risers and exhaust manifolds are also evidence leaks.  While the risers and manifolds permit a small amount of leakage due to their metal parts expanding and shrinking when they heat and cool, excessive leaks need to be investigated and exhaust risers and manifolds will need to be replaced periodically.


Engine Hoses

Hoses must be replaced right away when they start to crack as cracks lead to leaks and can cause severe engine damage.


Propeller Shaft Stuffing Box

Inspect the propeller shaft stuffing box for signs of leakage due the improper adjustment or wear and tear. Check the stuffing box while the boat is docked but still on the water.


Universal Joints, Shift cables, and Exhaust Bellows

Check the universal joint, shift cable and exhaust bellows on your outboard engine and replace as needed as u-joints and the rubber bellows that protect them are subject to wear and tear. Additionally, rubber bellows can also be damaged by debris in the water and animals. If damaged rubber bellows are not replaced, you boat can take on water and eventually sink.

Recommended Products: 

Mercury Quicksilver Bellows Adhesive

Mercury Quicksilver MerCruiser Brave 1, 2, 3, Outdrive to Bell Housing Install Gasket Kit

Mercury Quicksilver Bellows Adhesive


Gimbal Bearings

Usually a boat owner will suspect a gimbal bearing problem only after they have heard a “growling” noise from the transom or drive area. The growl will be more pronounced when the steering wheel is fully turned to one side or the Mercury Gimbal Bearingsother.

Once this noise is heard immediate action must be taken to prevent further damage. Gimbal bearings usually don’t just fail on their own. Water in the u-joint bellows or lack of lubrication are the two main causes Mercury Quicksilver 2-4-C Grease with PTFEof failure. Regular inspection and lubrication with Mercury Quicksilver 2-4-C 8oz Marine Grease Lubricant are great ways to prevent this failure and possible engine damage.

Featured Products:

Mercury MerCruiser Bravo & Alpha Transom Assembly Gimbal Bearing Kit

Mercury Quicksilver 2-4-C 8 oz Marine Grease Lubricant

Mercury Grease Gun

Mercury Quicksilver 2-4-C 14 oz Grease Gun Cartridge

Mercury High-Performance Extreme Grease

*Stock Up and Save* – Mercury Quicksilver 2-4-C 3 oz Grease Gun Cartridges Multipack

Engine Oil – Mercury Precision Lubricants

Boating is not often thought of as a harsh environment, but in fact it is one of the most FC W 25 W 40 Mercury Engine Oil.jpgdemanding environments in which an engine can operate.

Marine engines can and are often used for extended periods at wide-open throttle (up to 6400 rpm on some models), in harsh saltwater, and intense UV sunlight. Then, marine engines sit in storage over the off-season, in many cases without any use. Focusing on these demands, all Mercury Marine Precision Oils and Lubricants are specially engineered for the unique needs of marine engines and rigorously tested to meet our high standards, protecting your outboard and providing many years of engine life.

Featured Products:

FC-W 4-Stroke (25W-40) Oil – Quart – 92-8M0078627 – Gallon – 92-8M0078628

Synthetic Blend 4-Stroke (25W-40) Outboard Oil – Quart – 92-8M0078629 – Gallon – 92-8M0078630

4-Stroke (10W-30) Outboard Oil –  Quart – 92-8M0078625 – Gallon – 92-8M0078626 


High Performance Gear Lube

Mercury High-Performance Gear Lube is engineered to provide maximum protection for sterndrive and outboard lower units. Exclusive formula is engineered to provide extended gear life in extreme conditions including high-speed and high-horsepower applications. Extensively Mercury MerCruiser Bravo Drive High Performance Gear Lube Oil Kit.jpgtested to provide excellent protection against corrosion and excessive wear. Specifically formulated to help prevent failures due to water entering the gear housing. Extreme pressure synthetic additives protect gears from metal to metal contact. Since no industry-wide standards exist concerning marine gear oils, it is essential to use products such as Mercury High-Performance Gear Lube which has been specifically designed and tested for marine applications.

Featured Product: 

Mercury MerCruiser Bravo Drive High Performance Gear Lube Kit

The Good Old-Fashioned Smell Test

Open the engine compartment and check for smells that can indicate that there is a leak somewhere. If you smell fuel, there is a leak in the engine which is likely around fuel lines, fuel filters, carburetors and fuel tank fittings.  If you smell fuel immediately contact a qualified marine repair shop to inspect your engine.

Also, simple and regular fuel maintenance will add years to your engine’s life and will improve your engine’s performance.

Featured Products:

Mercury Precision Care Quickare – 12 ozFUEL CARE MERC HEADER.png

Mercury Precision Care Quickare – 32 oz

Mercury Precision Care Quickleen – 12 oz

Mercury Precision Care Quickleen – 32 oz

Mercury Precision Care Quickstor – 12 oz

Mercury Precision Care Quickstor – 1 gallon

Want to learn more about Mercury’s 3-step fuel treatment system? Click here to watch video, 

These simple and regular checks will keep your inboard engine in great shape for years to come. As always, PartsVu recommends utilizing your local boat dealer if you need assistance.



Topics: General Repair, Care & Maintenance,Mercury Maintenance