Frequently Asked questions

Every 100 hours or once yearly, whichever occurs first.

The major consideration in preparing your outboard for storage is to protect it from rust, corrosion, and damage caused by freezing water that may be trapped in the engine. We recommend taking your engine to an authorized Mercury dealer to perform the work. Damage from improper storage procedures is not covered under the Mercury Marine limited warranty policy. If you choose to perform the storage procedure, follow the storage procedures outlined in your Operation, Maintenance & Warranty manual.

Note: These are minimum engine specifications. Additional electrical loads from the boat will require larger batteries.

  • Four Stroke Models

  • 9.9/15 & 25

    465 Marine Cranking Amps (MCA) or 350 Cold Cranking Amps (CCA)

  • 30/40, 45/50

    -Operation Above 32°F (0°C) 465 Marine Cranking Amps (MCA) or 350 Cold Cranking AMPS (CCA) Operation Below 32°F (0°C)
    -1000 Marine Cranking Amps (MCA) or 750 Cold Cranking AMPS (CCA)

  • 75/90

    -Operation Above 32°F (0°C) 465 Marine Cranking Amps (MCA) or 350 Cold Cranking AMPS (CCA) Operation Below 32°F (0°C)
    -1000 Marine Cranking Amps (MCA) or 750 Cold Cranking AMPS (CCA) Ampere-Hours (Ah) 70 - 100

  • two Stroke Models

  • 6 - 15, 20/25, 30/40, 40/50 & 60

    465 Marine Cranking Amps (MCA) or 350 Cold Cranking Amps (CCA)

  • 75 - 125

    525 Marine Cranking Amps MCA) or 450 Cold Cranking Amps (CCA)
    V-6 Carb/EFI Models

  • V-6 Carb/EFI Models

  • 135/200 & 225/250

    630 Marine Cranking Amps (MCA) or 490 Cold Cranking Amps (CCA)

  • OptiMax Models

  • 2.5L/3.0L

    1000 Marine Cranking Amps (MCA) or 750 Cold Cranking AMPS (CCA)

Four-strokes have inherently cleaner running qualities over traditional two-strokes. They tend to have smooth and quiet operation, improved fuel efficiency, and don't smoke. These attributes provide consistent starting, better idle and trolling performance; and they reduce fuel consumption. A noticeable downside to most four-strokes is the reduction of low and mid-range torque.

Direct-injected two-strokes, particularly the Mercury Optimax, provide many of the same positive characteristics as four-strokes while maintaining the power and performance of a two-stroke. The Optimax also provides industry-leading fuel economy the best of any outboard.

The bottomline get advice from our sales and service professionals relative to your specific application.

Engine Oil.

For optimum engine performance and maximum protection, use the following oil:

  • Application

    Recommended Oil

  • All MerCruiser engines

    Mercury MerCruiser Full-Synthetic Engine Oil, 20W-40, NMMC FC-W rated

IMPORTANT: Lubrication requirements for catalyzed engines differ from the requirements for non-catalyzed engines. Some marine-grade lubricants contain high levels of phosphorus, which can damage the catalyst system on MerCruiser engines. Although these high-phosphorus lubricants may allow acceptable engine performance, exposure over time will damage the catalyst. Catalysts damaged by lubricants containing high levels of phosphorus may not be covered by the MerCruiser Limited Warranty.

If Mercury MerCruiser Full-Synthetic, 20W-40 oils is unavailable, use the following lubricants, listed in order of recommendation. If you are servicing a catalyst engine, use these for short periods of time only.

  1. Mercury/Quicksilver 25W-40 Synthetic Blend, NMMA FC-W-rated 4-cycle MerCruiser oil
  2. Mercury/Quicksilver 25W-40, NMMA FC-W-rated 4-cycle MerCruiser oil
  3. Other recognized brands of NMMA FC-W-rated 4-cycle oils
  4. A good-grade, straight-weight detergent automotive oil according to the last row of the operating chart below

NOTE: We do not recommend non-detergent oils, multi-viscosity oils (other than as specified), non-FC-W-rated synthetic oils, low-quality oils, or oils that contain solid additives.

This crankcase oil recommendation supersedes all previously printed crankcase oil recommendations for MerCruiser gasoline engines. The reason for this change is to include the newer engine oils that are now available in the recommendation.

Older Operation, Maintenance & Warranty manuals, Service manuals and other publications that are not regularly updated will not be revised to show this latest engine oil recommendation. Current Operation, Maintenance & Warranty manuals, Service manuals and other service publications that receive regular updates will receive this revised recommendation the next time they are updated.

While these add-on devices may reduce the time it takes to get the boat on plane, they may also cause or contribute to abnormal or even unsafe handling of the boat and failure of the anti-ventilation plate. Using a product often referred to as a stabilizer fin is a modification of the gearcase that may change the manner in which the boat operates on the water. With the unit trimmed fully down (in or under), a reduction of the time necessary to get a boat on plane may result. However, some V-bottom boats using a stabilizer fin may exhibit a tendency to roll over far to one side as soon as planing occurs. The direction and degree of the roll will be dictated by prop rotation, weight distribution, and degree of trim under. The boat roll can cause passengers to be ejected. Trimming up or out can reduce or eliminate the roll. Because it is not possible to know how a given boat will respond to the use of such a product without thorough testing, Mercury cannot recommend that such products be used or not used. Also, use of these products may cause or contribute to the failure of the anti-ventilation plate on the gearcase. Failures caused, or contributed to, by modification are not covered by the limited warranty.

Your outboard has control anodes at different locations. An anode helps protect the outboard against galvanic corrosion by sacrificing its metal to be slowly eroded away, instead of the outboard metals.

Each anode requires periodic inspection especially in saltwater applications, which will accelerate the erosion. To maintain this corrosion protection, always replace the anode before it is completely eroded. Never paint or apply a protective coating on the anode, as this will reduce its effectiveness.

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.

Every 300 hours or 3 years, whichever comes first.

Every 300 hours or 3 years, whichever comes first.

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.

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.

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.

In fact, Mercury recommends 25W40 in all cases except the small outboards at low temperatures. At lower temperatures, oil tends to become thicker, resulting in more friction. On manual-start models, this additional friction can have an affect on the pull force required for starting the outboard. The 10W30 oil has less friction at cold temperatures and therefore results in a lower pull force for easier starting.