Frequently Asked Questions

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MerCruiser Corrosion

Question:

When my boat is stored in the water, should my sterndrive be stored in the “up” or “down” position?

Answer:

Sterndrive should be stored in the down position to ensure that the anodes are in the water for maximum corrosion protection.

Question:

My sterndrive paint is peeling and/or blistering. What is going on?

Answer:

One of the first signs of galvanic corrosion is paint blistering (starting on sharp edges) below the waterline, with a white powdery substance forming on the exposed metal areas. As the corrosion continues, the exposed metal areas will become deeply pitted, with the metal actually being eaten away. Galvanic corrosion of aluminum sterndrive units, or any other underwater aluminum on your boat, is accelerated by attaching stainless steel components like propellers, trim planes (if connected to engine ground) and after-market steering systems. Whenever you add stainless steel accessories, it's a good idea to have the corrosion resistance checked to make sure it is still adequate.

Question:

What is the length of the corrosion warranty?

Answer:

The corrosion warranty is for three years from the original date of purchase of the complete power package for 1988 and newer MerCruiser product. SeaCore models receive a four-year limited corrosion warranty. See the complete corrosion warranty under the section titled Warranties or in your Operation, Maintenance & Warranty manual. Protection against certain types of corrosion damage must be provided by using such systems as the Mercury Precision MerCathode system and/or galvanic isolator. These certain types of corrosion damage include damage due to stray electrical currents (on-shore power connections, nearby boats, submerged metal), etc. It is the owner's responsibility to ensure that all necessary anti-corrosion devices are in good working order and are providing adequate protection.

Question:

What is a galvanic isolator and what does it do?

Answer:

The Mercury Precision Galvanic Isolator is a solid-state device that is series connected in line into the boat's green safety grounding lead ahead of all grounding connections on the boat. This device functions as a filter, blocking the flow of destructive low voltage galvanic (DC) currents, but still maintaining the integrity of the safety grounding circuit. A galvanic isolator is only necessary on boats utilizing a shore power connection.

Question:

What do I need to know about corrosion?

Answer:

The good news is that corrosion can be prevented! Marine corrosion is a fact of boating life, but you can protect your investment with diligence & proper maintenance. As the boat owner, YOU are the most important key to effective corrosion protection. Here are some things you should know:

All MerCruiser sterndrives come standard with aluminum sacrificial anodes a three-year warranty against certain types of corrosion (see your Operation, Maintenance and Warranty manual for more details). SeaCore models receive a four-year limited corrosion warranty.

Bravo sterndrives are also equipped with a MerCathode, optional on Alphas.

Magnesium anodes are suggested for fresh water use ONLY & can be purchased from your authorized dealer.

Anodes & sterndrives should be inspected on a regular basis for signs of corrosion. Do not paint anodes.

Not all anodes are created equal. Don't sacrifice your sterndrive's protection with the use of poor-quality aftermarket anodes.

The MerCathode should be tested annually by an authorized dealer for proper operation. Do not paint or power-wash the MerCathode.

Your particular boating environment may require that you install additional anodes or other protective devices.

Whenever you add stainless steel accessories (for example props or trim tabs) it's a good idea to have the corrosion resistance checked to make sure it is still adequate

If you use shore power, you should have an approved galvanic isolator installed to protect against stray current corrosion (electrolysis) from your dock, from your boat's accessories or from other nearby boats.

Corrosion can be caused by many factors, such as the wrong type or improper application of anti-fouling paint, marine growth, stray electrical current (electrolysis), an improperly wired or damaged MerCathode, etc. These types of conditions are not covered by the warranty.

Before you notice signs of corrosion, contact your authorized MerCruiser dealer to arrange for an in-the-water hull potential test where the boat is primarily moored. This test will help the dealer determine if your protection level is adequate.

See your Operation, Maintenance & Warranty manual for more information.

A very informative pamphlet on corrosion "Marine Corrosion Protection Guide" (#90-88181301) is available. Please call 1-800-MERCURY to request one.

Question:

What is a MerCathode and what does it do?

Answer:

The Mercury Precision MerCathode system provides automatic protection against galvanic corrosion. It is a solid-state device that operates off a boat's 12-volt battery and provides protection by impressing a reverse blocking current that stops the destructive flow of galvanic currents. If your power package does not come already equipped with a MerCathode system, Mercury strongly recommends that you install one, particularly if your boat is equipped with a stainless steel propeller or other submerged stainless steel hardware. The MerCathode should be tested annually by an authorized dealer for proper operation.

MerCruiser Storage

Question:

What is the warranty on parts?

Answer:

Genuine Mercury or Quicksilver Precision Parts carry a limited 12-month warranty against defects in materials and workmanship. For specific details, contact your local dealer.

Question:

My dealer is recommending that I shrink wrap my boat before storage. Are there any items affecting my engine that I should be concerned about?

Answer:

Shrink wrap is a very effective method of protecting the boat during periods of storage; however, it is very important to ventilate the hull. Even in the driest conditions, without ventilation, the plastic cover will trap moisture. This moisture can create rust on some metal components, corrosion on others and mold/mildew on the carpet and upholstery. Always follow the manufacturer's recommendations for ventilation.

Question:

Should my sterndrive be stored in the up or the down position?

Answer:

If you store your sterndrive installed on your boat, you should keep it in the down position. Otherwise, the rubber bellows in the transom assembly can become permanently deformed and fail.

Question:

Can I use propylene glycol (RV antifreeze) in my engine?

Answer:

Propylene glycol antifreeze with a rust inhibitor is approved for use in the raw water cooling system for cold weather storage purposes ONLY. However, if your engine is equipped with a closed cooling system, you should always use a 50/50 mixture of ethylene glycol antifreeze and water in this system. Even if you don't live in a freezing climate, you should still use an antifreeze/water mixture rather than plain water. Antifreeze mixtures have superior anti-corrosion and boil over protection properties.

Question:

How many drain plugs are on my engine and where are they located?

Answer:

It depends on which drain system your engine is equipped with.  For specific information and product identification, check with your local authorized dealer.

Question:

How often should spark plugs be changed?

Answer:

Every 300 hours or 3 years, whichever comes first.

Question:

What should be done when storing boats with ethanol-blended fuels for extended periods?

Answer:

Follow the instructions for normal storage preparation found in the Operation, Maintenance & Warranty manual. When preparing to store a boat for extended periods of two months or more, it is best to completely remove all fuel from the tank. If it is difficult or not possible to remove the fuel, maintaining a full tank of fuel with a fuel stabilizer added to provide fuel stability and corrosion protection is recommended. It is best to add the stabilizer and fuel treatment to the tank at the recommended dosage, run the engine for 10 minutes to allow the system to be cleaned, shut off the fuel valve to interrupt the fuel supply and allow the engine to run until it stops, and top off the tank until it’s full to reduce the amount of exchange with the air that might bring in condensation. Do not cap the tank vent and do not fill with fuel to the point of overflowing. Some extra space should be maintained in the tank to allow for expansion and contraction of the fuel with temperature changes. A partially full tank is not recommended because the void space above the fuel allows air movement that can bring in water through condensation as the air temperature moves up and down. This condensation could potentially become a problem.

Mercury Marine Quickstor can help maintain fuel systems in storage. It contains oxidation inhibitors to reduce oxidation and gum formation, metal-chelating agents to protect metal components from corrosion, water-absorbing agents to reduce the presence of free water, and dispersants to help suspend and disperse debris. When placing the boat back in service, be sure to reopen the fuel valve to the engine.

Question:

Can I leave my lower unit or sterndrive empty of lubricant over the winter?

Answer:

We do not recommend leaving a lower unit or sterndrive empty during storage periods. An empty oil cavity may allow moisture to collect on the gears, bearings and shafts. Rust will form when the moisture reacts with the air, damaging the internal components.

Note: If water was present when draining the gear oil, the lower unit or sterndrive should be inspected by an authorized dealer.

Click here for tips on winterizing.

Question:

Do I need to put antifreeze into the raw-water/seawater section of the cooling system after draining?

Answer:

MerCruiser requires the use of propylene glycol antifreeze (with a rust inhibitor for marine engines) in the seawater section of the cooling system. Damage caused by freezing or improper winterization is not covered by the limited factory warranty. 

Click here for tips on winterizing.

Question:

Do I still need to have winterization performed by my dealer if I have a self-drain system on my engine?

Answer:

The drain system on your engine is NOT intended to replace full winterization. It is for extending your boating season by allowing the cooling system to be drained after use if there is a risk of light freezing weather and you will be boating the next day. For full extended winter storage, after completely draining the cooling system, Mercury MerCruiser requires the use of propylene glycol antifreeze (with a rust inhibitor for marine engines) in the seawater section of the cooling system. The fuel system must have fuel stabilizer added and the system must be fogged with 2-cycle oil. We recommend that your product be winterized by an authorized MerCruiser dealer. Damage caused by freezing or improper winterization is NOT covered by the limited factory warranty. This is also a good time to have scheduled maintenance performed on your engine by your dealer.

Click here for tips on winterizing.

MerCruiser Maintenance

Question:

How often should I flush my engine in saltwater use?

Answer:

For maximum corrosion protection, we recommend that the engine be flushed with freshwater after each saltwater use.

Question:

My Operation, Maintenance & Warranty manual lists the oil capacity for my engine, but when I change the oil it won't take that much without being overfilled. Why?

Answer:

The engine oil capacities given in the Operation, Maintenance & Warranty and Service manuals are approximate and indicate what the capacity of the entire lubrication system is. A small amount of oil remains in the crankcase, oil lines, etc. This is why it is difficult to get the indicated amount of oil in the engine without it being overfilled. You should always fill the crankcase according to the dipstick when the engine is level, preferably with the boat at rest in the water. If the oil is at the full mark on the dipstick, then it is at the proper level regardless of how much you put in. It is important not to overfill or under fill the crankcase. The engine oil level should always be between the add and the full marks on the dipstick. 

Question:

Where do I find maintenance and lubrication information for my engine?

Answer:

The Operation, Maintenance & Warranty manual outlines the typical maintenance and lubrication items. If your manual is missing or damaged, please order online or through any authorized Mercury dealer. Please have your outboard or sterndrive serial number before placing the order.

Question:

How can I obtain parts or service for my Quicksilver generator?

Answer:

You can contact the Generac Corporation for this information at 1-800-333-1322.

Question:

Do you have any tips for do-it-yourself maintenance?

Answer:

If you are a person who likes to do-it-yourself, here are some suggestions for you:

Your MerCruiser power package is an advanced technological piece of machinery. Electronic ignition and special fuel delivery systems provide greater fuel economies, but are also more complex for the untrained technician.

Do not attempt any maintenance or repairs which are not covered in the service manual unless you are aware of the precautions and procedures required. Your safety is very important to us.

The service manual is written for the trained technician. Do not attempt repairs if you do not understand the procedures.  

There are special tools and equipment that are required to perform some repairs. Do not attempt these repairs unless you have these special tools and/or equipment.

Please do not contact the dealer, customer service office, or the factory to request troubleshooting help or to request the repair procedure. It is difficult to diagnose a problem over the telephone.

Remember, your authorized dealer is there to provide service for your power package. Dealers have qualified, factory-trained technicians.

Question:

Why do I have to periodically check my engine alignment and lubricate the engine coupler?

Answer:

With time and usage, the engine will sometimes get out of alignment with the transom assembly and sterndrive. For longest engine coupler life, it is important that the engine alignment be as accurate as possible. We recommend using Quicksilver Engine Coupler Spline Grease for proper lubrication. Damage caused by improper engine alignment or lack of lubrication is not covered under the limited warranty.

Question:

Do you have a freshwater flush kit to flush the engine while the boat is in the water?

Answer:

Currently we offer flush kits for all 1988 and newer MerCruiser engine applications. And, we now offer kits that can be used with Bravo sterndrive, inboard, and towsport engines when the boat is in or out of the water. The flush attachment kit for Alpha engines can only be used when the boat is out of the water.

In all applications, the engine must be running when using a flush kit. See your MerCruiser dealer for details on the appropriate kit and additional components that will fit your engine and best suit your needs.

Question:

Where can I get factory Service manuals, Parts manuals, or Operation, Maintenance & Warranty manuals?

Answer:

You can order all available literature online. You could also order all literature through any authorized Mercury dealer. Please have your outboard or sterndrive serial number before placing the order.  You can also order manuals through our Publications department by calling 920-929-5110.

Question:

How often should I change my sacrificial anodes?

Answer:

Because they are self-sacrificing, the anodes must be inspected often and replaced when 50% consumed. Anodes may also become coated (calcified) with a white chalky coating or marine growth. Either of these will prevent the anode from sacrificing itself and, therefore, prevent it from protecting your drive and other underwater components. Use sandpaper to remove any coating. DO NOT use a wire brush.

Question:

How often should maintenance be performed?

Answer:

Maintenance intervals vary depending on the specific engine and drive model. Recommended maintenance intervals are included in your Operation, Maintenance & Warranty manual or service manual.

Question:

How often should coolant be changed on engines with closed cooling?

Answer:

Every 5 years.

For optimum performance and maximum protection use Mercury /Quicksilver Extended Life Coolant / Antifreeze.

Question:

The paint on the top of my sterndrive is dull and seems to have some type of deposit adhering to it. How can I make it look nice again?

Answer:

The dullness comes from mineral deposits in the water. When the boat is on plane, the top portion of the sterndrive is out of the water. As the water evaporates from the top of the sterndrive, it leaves behind mineral deposits. You can remove them by using a liquid cleaner for bathroom tub and tile, followed by a coat of wax to help protect the surface.

Question:

Is it better to change my engine oil/gear lube at the beginning or end of the season?

Answer:

It is better to change the oil and gear lube at the end of the season, prior to storage. Lubricants naturally accumulate moisture, combustion by-products, and other contaminants during use. It can be detrimental to store an engine or drive with large amounts of these contaminants present.

Question:

What kind of spare parts should I carry on my boat for my MerCruiser?

Answer:

Some suggested items would include a floating prop wrench, a spare prop and attaching hardware, spark plugs, belt(s), oil, power trim and steering fluid, High Performance gear lube, water separating fuel filter, and appropriate fuses.

Question:

What type of fluid should I use in my power trim system?

Answer:

Mercury/Quicksilver Power Trim and Steering Fluid – part # 92-858074K01

Question:

How often should spark plugs be changed?

Answer:

Every 300 hours or 3 years, whichever comes first.

Question:

Should I use Premium Blend or High Performance gear lube in my sterndrive?

Answer:

Mercury High Performance gear lube is recommended for use in all sterndrives.

Question:

How often should my seawater pump impeller be serviced?

Answer:

Every 300 hours or 3 years, whichever comes first.

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