Mercury MerCruiser 100 & 300 Hour Service Kits

MerCruiser Maintenance Kits - Resources and Information

We’re proud to offer genuine MerCruiser 100 & 300 Hour Marine Engine Service Kits for virtually every MerCruiser model. These kits take the guesswork out of finding the right outboard oil filters, drain gaskets, spark plugs, lube, water pump parts, and more by combining all the outboard parts into one convenient package. 

Choose from the following MerCruiser 100 hours service kits and Mercury 300 hour service kits to keep your MerCruiser performing 

• 2.5L MerCruiser 100 & 300 Hour Service Kits
• 3.0L MerCruiser 100 & 300 Hour Service Kits
• 4.3L MerCruiser 100 & 300 Hour Service Kits
• Alpha & Bravo Drive MerCruiser 100 & 300 Hour Service Kits
• 4.5L MerCruiser 100 & 300 Hour Service Kits
• 5.0L MerCruiser 100 & 300 Hour Service Kits
• 5.7L MerCruiser 100 & 300 Hour Service Kits
• 6.2L MerCruiser 100 & 300 Hour Service Kits
• 8.2L MerCruiser 100 & 300 Hour Service Kits
• GM V6 & V8 MerCruiser 100 & 300 Hour Service Kits

To assist you in performing regular maintenance on your MerCruiser engine, we’ve put together helpful resources, including: 

• MerCruiser Inboard Maintenance
• MerCruiser Maintenance Parts Library
• Mercury Outboard and Mercruiser Resources Collection

If you have some parts and supplies on hand, or only needing a few things here and there, PartsVu stocks a complete range of MerCruiser parts and other service kits to help you service your MerCruiser motor. Choose from the following Mercury MerCruiser parts:

• MerCruiser Oil Change Kits
• MerCruiser Filters
• MerCruiser Lubes - Oils - Additives
• MerCruiser Ignition
• Mercury Marine Paint
• MerCruiser Service & Owner Manuals
• MerCruiser Propellers & Propeller Hardware
• MerCruiser Drive System
• MerCruiser Electrical System
• MerCruiser Fuel System
• MerCruiser Cooling System
• MerCruiser Exhaust System
• MerCruiser External Engine
• MerCruiser Internal Engine
• MerCruiser Transom
• MerCruiser Power Trim
• MerCruiser Rigging - Steering - Gauges - Throttle Control

MerCruiser Service Kits FAQ

How do you grease a MerCruiser motor?

Greasing your MerCruiser is an important part of keeping the motor functioning and preventing excessive wear on high-friction areas. Plus, it’s an essential part of your 100-hour and 300-hour service intervals that helps preserve your MerCruiser warranty.

To grease your MerCruiser motor, load a tube of Mercury grease into the grease gun and use a trigger-activated plunger to slowly dispense the grease directly into the grease points.

Grease points are metal fittings attached to your outboard motor that allow grease to be fed into the system under moderate to heavy pressure. Because you don’t have to remove most engine components to access the grease points, they’re easy to work with. 

If you’re not sure where to find grease points on your Mercury MerCruiser, refer to your service manual for your particular MerCruiser model outboard and add grease where specified.

How do you perform a MerCruiser leak-down test?

An outboard leak down test is a simple diagnostic checkup for your MerCruiser – and should be incorporated into your regular maintenance intervals for peace of mind as well as when you believe your MerCruiser isn’t performing as well as it once was.

A MerCruiser leak-down test indicates the condition of each of the MerCruiser engine’s cylinders and the overall condition of the motor. Similar to a compression test, it involves spraying compressed air into each cylinder and using a pressure gauge to measure a percentage of pressure that’s lost after a short period.

Part of performing a leak-down test on your MerCruiser motor is to listen for any signs of leakage. By listening closely to each cylinder and the areas around them, you’ll better understand where leaks may be present.

• Step #1: Carefully remove the top cowling, Then, remove the ignition coil cover at the rear of the motor.
• Step #2: Remove the spark plugs. 
• Step #3: Remove the flywheel cover from the top of the motor.
• Step #4: Mark the flywheel with a marker at 0°, 120°, and 240°. These positions indicate where you’ll rotate each pair of cylinders to the top dead center positions (see Step #11 and #12 below).
• Step #5: Rotate the crankshaft with your ratchet and socket to the top dead center for cylinder #1.
• Step #6: Adjust the regulator on the leak down tester to 0% to calibrate it for an accurate reading. 
• Step #7: Connect the leak down tester by screwing into the spark plug port at cylinder #1. Next, connect the tester to the compressor and take a measurement. Be sure to firmly hold the crankshaft to prevent it from rotating.
• Step #8: Rotate the crankshaft 360° (one full rotation) to put cylinder #4 at top dead center.
• Step #9: Connect the leak down tester to cylinder #4. Then, take a measurement while holding the crankshaft to prevent it from rotating.
• Step #10: Set cylinder #3 to top dead center at the 120° mark. Next, repeat step #7 through Step #10 for cylinders #3 and #6.
• Step #11: Set cylinder #2 to top dead center at the 240° mark. Then, repeat step #7 through Step #10 for cylinders #2 and #5.
• Step #12: Replacement is the same as disassembly. Be sure to replace spark plugs in numbered order and apply anti-seizing compound on the threads for easy removal/replacement in the future. Also, firmly reattach the ignition wires for a solid connection.

What are the most common MerCruiser problems?

The MerCruiser line features a solid line-up inboard, inboard-outboard, outboard, and sterndrive motors. Even though MerCruisers receive consistently high marks for reliability, longevity, and performance, continual usage and exposure to the elements can dramatically wear out MerCruiser parts and internal components. Because of this, regular maintenance and servicing are required to keep this outboard motor in the water and out of the shop.

The following are 4 of the most common MerCruiser 4-stroke outboard problems: 

1. Faulty Head Gasket - Over time, the MerCruiser head gasket is regularly exposed to a number of elements that reduce its integrity, such as salt water, heat, fuel, and other substances. Once a head gasket fails, water and other contaminants will enter your engine. When it comes to MerCruiser problems, replacing the head gasket should be a priority every 4 years of service, or sooner if usage exceeds the average boater (50 hours per season, or 200 hours for 4 years).
2. Bad Fuel Pump - A bad MerCruiser fuel pump is one of the most common problems for MerCruiser engines. Fuel pumps generally malfunction over time, and when the fuel pump finally gives out, your motor is essentially dead in the water until it is fixed. Fortunately, bad fuel pumps are easy to replace and repair. They’re also relatively inexpensive when compared to other necessary engine repairs. 
3. Clogged Fuel Injectors - If your MerCruiser features fuel injection instead of a carburetor, carbon will eventually build-up in each of the individual fuel injectors to prevent a smooth distribution of fuel. When carbon clogs the fuel injector, your outboard will often misfire, vibrate excessively, and bog down during idle or when the throttle is applied - not to mention a noticeable drop in fuel economy. Cleaning your fuel injectors with fuel injector cleaner keeps clogging from occurring and your MerCruiser motor performing at its best.
4. Trim and Tilt Problems - A faulty trim and tilt switch can prevent you from the fine-tuning (trim) and dramatic changes (tilt) needed for optimal performance of your MerCruiser. Luckily, you can avoid these problems by swapping out the trim and tilt switch on your MerCruiser motor.

How do you perform a MerCruiser motor oil change?

Performing needed maintenance in a timely manner on your MerCruiser is the key to its overall longevity and reliability. The procedure isn’t complicated but can get messy if you don’t know what you’re doing. 

1. Loosen your oil filter to help vent the system.
2. Remove your dipstick, insert your oil pump, and once your oil pump is inserted into the dipstick tube, pull the oil out into your oil capture container.
3. Remove the old oil filter the rest of the way.
4. Prep the new filter for installation by applying a light film of oil onto the face seal of the Mercruiser oil filter.
5. Thread the oil filter onto the oil filter mount and hand tighten.
6. Remove your Mercruiser’s fill cap and insert your funnel to prepare to add the new oil.
7. Fill the engine with the recommended oil with the proper quantity of oil—4.5 liters for a 4.5L sterndrive and 4.7 liters for a 6.2L sterndrive. We recommend using Mercury 25W-40 Synthetic Blend Oil; however, you can use Mercury 25W-40 oil.
8. It’s a good idea to run the engine with the proper water supply to check for any leaks and make sure that the proper oil level is maintained.
9. For more detailed information regarding these maintenance steps and to verify any details that may pertain to your specific engine model, please refer to your Mercury Mercruiser owner’s manual.

To avoid a big mess, use one of our MerCruiser service kits to perform a quick and easy MerCruiser oil change.

Are all oil filters the same?

No, not all MerCruiser parts are created equal - and MerCruiser oil filters are no exception. Only OEM MerCruiser oil filters are manufactured specifically to protect MerCruiser engines, using the finest components and construction methods available. This includes using special filter media and metal filter media bases (instead of cardboard), to create oil filters capable of greater durability and filtration. From the quality of the materials used to their high-quality construction, MerCruiser oil filters outperform and out-protect aftermarket marine engine oil filter alternatives.

Is winterization a part of regular maintenance?

Yes, winterization is part of regular Mercury MerCruiser maintenance, though you’ll only be tasked with putting it away for the season once. 

The primary distinction between regular maintenance and winterization is that winterization involves maintenance when your MerCruiser is NOT in use. However, the long months of sitting in storage have the potential to permanently damage your MerCruiser engine and component.

To learn more about what winterizing your Mercury Mercruiser entails, refer to our How to Winterize a MerCruiser Sterndrive article.