MerCruiser Winterization FAQs

How can I find my closest authorized MerCruiser dealer?

Authorized MerCruiser dealers in the United States and Canada can be found under Find a Dealer on this website.

Links to regions outside of the United States and Canada can be found on the Contact Us page.

How often should spark plugs be changed?

Every 300 hours or 3 years, whichever comes first.

How do I winterize my MerCruiser product?

Because of variations in models, it is not possible to include this information for all of our products on this website. We recommend that you have this procedure completed by an authorized dealer. The raw water section of the cooling system must be COMPLETELY drained for winter storage, or immediately after cold weather use, if the possibility of freezing temperatures exists. As manual multi-point drain systems can have as few as three blue drain plugs and as many as seven, MerCruiser recommends referring to your Operation, Maintenance & Warranty manual or Service manual for the type of drain system you have. Draining of the seawater section of your engine does not mean it is winterized, MerCruiser requires that propylene glycol antifreeze be used in the seawater section to insure protection from freeze damage. Failure to do this may result in trapped water causing freeze and/or corrosion damage to the engine. Damage caused by freezing or improper winterization IS NOT covered by the MerCruiser limited warranty.

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

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.

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

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.

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

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

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

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.

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

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.

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

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.

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?

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.

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

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.