MerCruiser 4.5L MPI Alpha Service Parts

MerCruiser 4.3 MPI Bravo Parts - Resources & Information

Based on the General Motors 262-cubic-inch-displacement block, the 4.3-liter V-6 sterndrive has propelled boats for more than 25 years. MerCruiser still offers two iterations, with a choice of Alpha or Bravo drive. Features like an integrated water pump and permanently lubricated pivot points let you spend less time on maintenance and more time boating.

As one of the most powerful sterndrive motors of the MerCruiser line, the MerCruiser 4.3L MPI Bravo series is renowned for its year-after-year reliability, exceptional 220 HP performance, and longevity. 4.3 MerCruiser MPI stands for “Multi-Point Fuel Injection”, which means this 4.3 liter boat engine features a fuel system that uses a fuel injector at every intake port of the engine for more consistent fuel delivery and 4.3 liter MerCruiser horsepower. 

Over time, however, these MerCruiser motors degrade due to harsh aquatic environments, heavy usage, and the lifespan of components. To keep your MerCruiser 4.3L MPI running reliably year after year, it’s important to understand your MerCruiser inside and out. That’s why PartsVu offers so many useful resources to help you maintain your MerCruiser 4.3L MPI every step of the way. 

Whether you’re looking to change your lower unit oil, replace your old filters, or troubleshoot with a 4.3 L MerCruiser engine diagram, PartsVu helps you get the job done and enjoy worry-free boating. 

To help you find the right MerCruiser 4.3L MPI parts plus in-depth articles for reference, check out some of our helpful MerCruiser resources and the FAQ below:

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

MerCruiser 4.3L MPI Service Parts FAQ

Is winterizing my MerCruiser 4.3L MPI important?

While it’s always a bit more fun to pull out your boat than to put it away, properly winterizing your MerCruiser engine should be mandatory for all experienced boaters. Winterizing helps avoids engine damage and will facilitate a smoother start to the beginning of next season - after all, no one wants to wait to get back on the water!

There are several important steps you should take when storing your MerCruiser lower unit to ensure that it’s properly winterized.

1. Flush Your Engine - Thoroughly flush your MerCruiser engine to remove any salt buildup if you are a saltwater boater, or accumulated mud and grime if you are a freshwater boater. Failure to remove this debris from your MerCruiser lower unit leads to corrosion in the engine. And if you’re a saltwater boater, leftover salt crystals in the lower unit can act like sandpaper to your internal engine components.
2. Stabilize Your Fuel System - It is vital to use a fuel stabilizer like Quickstor Fuel Stabilizer when your boat will be sitting unused for more than two or three months. Add the amount of fuel stabilizer directed on the product’s packing to your fuel—for instance, 1 ounce of MerCruiser Fuel Stabilizer and Conditioner Plus for every gallon of gasoline, assuming the engine will be stored for more than 2 months. 
3. Fog Your MerCruiser Engine - Mercury Storage Seal Fogging Oil is a wax-based oil that coats the engine to prevent corrosion.
4. Change Out the Lower Unit Oil - We strongly recommend changing your MerCruiser gear lube before storage to make sure that there is no water in the lower unit’s oil. Any water in the oil could freeze, expand, and crack your lower unit. Also, changing lower unit oil means one less thing to do at the beginning of next season.
5. Disconnect Your Battery - Disconnect your battery and spray CRC Marine Battery Terminal Protector on your battery terminals.

How do I prepare my MerCruiser 4.3L MPI at the start of a new season?

After the cold season is finally over, it’s time to break out your MerCruiser motor again. However, there are a few tasks you’ll need to perform before putting your outboard back in the water for optimal performance: 

1. Uncover & Unwrap - Before you fold up your engine cover and store in a trash bag, the engine cover fabric itself should be cleaned. To do so, use a soft brush and a canvas-friendly cleaner like Star Brite Sail & Canvas cleaner.
2. Perform a Complete Walk-Around Inspection - With the cover off the boat, the next step in MerCruiser season breakout is to perform a walk-around inspection. Check for any leaks under the boat, specifically below the engine. Gear lube, engine oil, trim fluid, and gasoline are possible causes for any leaks or stains. Also, trust your gut - if something seems different than when you stored it, take a look to determine if any damage occurred. 
3. Protect Your Boat from Harmful UV Rays - UV rays can degrade your boat’s shine and even cause damage given enough time. Consider applying a coat of wax to protect your boat from UV rays. If you noticed your hull has a chalky appearance, applying a polishing compound before waxing brings out a bright, attractive shine.
4. Battery & Electrical System Assessment - If you removed or disconnected your batteries for storage during the offseason, it’s time to reconnect them. Before you do, visually inspect batteries for evidence of any physical deformation, leakage, corrosion, and age, especially around the terminals.
5. Inspect the Bilge Pumps, Float Switches & Fresh Water Systems - Float switches and bilge pumps are critical safety gear that is absolutely essential for worry-free boating in the new season. Properly wired float switches should function with or without the battery switch being turned on, so be sure to check both ways. Most boats are also wired so that the operator can manually toggle the bilge pump on. Check to see if the pump runs properly and that your bilge wiring, discharge hose, hose clamps, and thru-hull fitting are all in great shape. If your boat’s freshwater system was winterized, be sure to fill your tanks and flush antifreeze from the system, and dispose of it per the manufacturer’s recommendations. Consider a product like Spring Fresh to flush the freshwater system and clean the lines of any remaining antifreeze.

How do I perform maintenance for my MerCruiser 4.3L MPI?

Your MerCruiser 4.3 6 cylinder engine components need regular servicing during the lifespan of owning your motor. There are regular 4.3 MerCruiser maintenance intervals that must be met for Mercury engines, including 20-hour service, every 100 hours, 300 hours, and so forth. This includes inspecting, testing, and replacing MerCruiser 4.3 L parts to preserve optimal operation as well as your Mercury MerCruiser warranty. 

The following is Mercury’s maintenance schedule for 100 hour and 300 hour maintenance intervals, including external engine maintenance and all other required tasks: 

100 Hours/1 Year

300 Hours/3 Years

How do I use outboard schematics for my 4.3 MPI MerCruiser?

If you’re looking for in-depth information for maintaining and repairing your MerCruiser motor, PartsVu offers MerCruisers Engine Schematics and our helpful article, “How to Select the Right MerCruiser Parts”. You can find everything you need, from a MerCruiser 4.3 cooling system diagram, a complete 4.3 MerCruiser engine diagram, and everything else you need to maintain your MerCruiser. 

Start at the Mercury MerCruiser schematics page. Once there, you will choose the right 4.3 MerCruiser parts for your MerCruiser by searching either by your outboard’s Primary Identification Number (PID) located at the top of this page or look up your model using a series of dropdown menus on the left side of the page.

How do I select the right MerCruiser 4.3 parts for my marine engine?

PartsVu’s Mercury MerCruiser Maintenance Parts Library is the perfect reference when you need to replace common parts for MerCruiser 4.3. That’s because these 4.3 MerCruiser performance parts charts make it simple to find the right parts for your particular engine to perform regularly-scheduled maintenance. Additionally, find your MerCruiser cooling system diagram in your MerCruiser Owner’s Manual - an invaluable resource when choosing the right parts, matching your motor with the 4.3 MerCruiser engine diagram, and ultimately repairing your outboard. 

For MerCruiser motors, the first maintenance interval comes at 20 hours, then you’ll perform maintenance after 100 hours of service or one year of operation (whichever comes first). More extensive service is recommended after reaching 300 hours of service or three years, so the 100 hours addresses components that receive more wear and tear (such as fuel filters and oil filters).

After this period, maintenance is often more regular as the engine ages and parts wear out. For example, 1,000 hours generally requires an in-depth assessment by a qualified mechanic. Also, if you’re usually running your Mercury outboard in a more demanding manner, the manufacturer recommends more frequent servicing.

When selecting the correct Mercury Outboard Parts, there are some essential things every boater must keep in mind before purchasing and installing parts:

• Choosing MerCruiser OEM parts (original equipment manufacturer) over after-market parts often yields better long-term results for your engine as these components and products are specifically designed to meet the precise tolerances of Mercury engines.

• Check (and recheck) to ensure that you have the exact part number that matches your Mercury outboard engine. It’s important to do this because Mercury has many MerCruiser engine models that look very similar but contain slight differences in performance. Therefore, unmatched parts may not fit uniformly, leading to malfunctions, underperformance, and severe engine damage.

• Proper maintenance is essential when it comes to extending the life of your Mercury outboard motor and should always be mandatory to retain the value of your outboard motor. While Mercury outboards are built to last, hazards like salt water, humidity, excessive heat, electrolysis, and demanding usage eventually take their toll on your motor.
• Proper storage for your Mercury outboard is required to preserve your motor for the long term. Failure to properly winterize your Mercury outboard can cause components to degrade while the engine sits and is exposed to the elements. Therefore, properly store your outboard when it is not in use.

For even more information, read our article, How to Select the Right MerCruiser Parts to make the right decisions in complete confidence for worry-free boating.