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Synthetic Marine Oil - 2-Stroke, 4-Stroke, and Diesel

As fun as it is to own a boat, they can create several headaches if you neglect maintenance. As well, some boaters and anglers don’t realize it, using a dedicated marine motor oil is vital to protecting marine motors.

Why use a dedicated marine motor oil?

AMSOIL marine motor oil protects in demanding operating conditions, from rust and corrosion, and fuel contamination.

Demanding operating conditions

Marine motors are characterized by high-rpm operation that can shear the molecular structure of oil and reduce its ability to protect against wear. On average, a marine motor propelling a boat 30 mph operates at 5,000 rpm, while an automotive engine powering a car 60 mph operates around 2,000 rpm. The added heat and stress invite wear and deposits. Heavy deposits can cause piston rings to stick, leading to compression loss and reduced power. Stuck rings can also lead to severe piston scuffing.

Rust and corrosion lead to wear

Marine motors are constantly exposed to humid air. The moisture the motor ingests increases the likelihood of corrosion compared to automotive engines. Water-cooled marine motors also run at lower temperatures than air-cooled engines, so moisture in the oil doesn’t evaporate as readily. Plus, when the motor is shut down for the day, moist air continues to enter the engine as it cools, increasing the risk for corrosion, especially if the oil doesn’t contain anti-corrosion inhibitors.

Fuel can contaminate the oil

Outboard motors typically use lake or river water for cooling. When you start the motor, it immediately draws cold water into the cooling system and circulates it throughout the motor. Compared to an engine with a closed cooling system, meaning one that uses a radiator and coolant, it takes longer to warm-up. A colder engine prevents the rings from sealing completely. More clearance between the ring and cylinder wall allows fuel to leak into the oil sump of four-stroke engines, diluting the oil and reducing its ability to protect against wear.

2-Stroke Synthetic Marine Oil

For two-stroke engines, wear protection and engine cleanliness are key. Oils with inadequate detergency can allow deposits and ring sticking, which robs your engine of power. Today’s engines run hotter than their predecessors, so using an oil that delivers excellent wear protection is also vital.

DOMINATOR™ Synthetic 2-Cycle Racing Oil (TDR)

DOMINATOR, an AMSOIL exclusive formulation, lubricates and protects high performance two-cycle motors, both on and off the track. High performance motors, particularly those that are modified, operate hotter and at higher RPMs than recreational motors, and they need good oil for peak performance. DOMINATOR is engineered for racing. It has the right... read more

Brand: AMSOIL • Product Code: TDR

DOMINATOR™ Synthetic 2-Cycle Racing Oil (TDR)Pricing Information or Place Order

HP Marine Synthetic 2-Stroke Oil (HPM)

The High-Performance Marine 2-Stroke Oil. Excellent for Evinrude® E-TEC™ factory-lean setting (replaces Evinrude XD100™ 2-Cycle Oil) Helps prevent deposits. Protects against wearLow smokeProtects against rustLow aquatic toxicity. Superior performance as an injection oil or at 50:1 pre-mixHigh-quality motor oil is critical... read more

Brand: AMSOIL • Product Code: HPM

HP Marine Synthetic 2-Stroke Oil (HPM)Pricing Information or Place Order

INTERCEPTOR™ 2-Cycle Oil (AIT)

Two-stroke powersports equipment is meant to be ridden hard. Repeatedly pushing a machine to wide-open throttle during all-day, aggressive riding, however, takes its toll on the engine. INTERCEPTOR Synthetic 2-Stroke Oil is specifically designed for reliability and longevity in hard-ridden snowmobiles, dirt bikes, ATVs and PWCs, helping enthusiasts.... read more

Brand: AMSOIL • Product Code: AIT

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Outboard 100:1 Pre-Mix Synthetic 2-Stroke Oil (ATO)

Specifically designed for outboard motors, Outboard 100:1 Pre-Mix Synthetic 2-Stroke Oil contains a heavy dose of low-temperature dispersant additives that excel at reducing varnish and carbon deposit formation in water-cooled motors. Its low-smoke, low-odor, low-toxicity properties produce fewer emissions at 100:1 mix ratios than oils mixed at 50:1... read more

Brand: AMSOIL • Product Code: ATO

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Synthetic 2-Stroke Injector Oil (AIO)

AMSOIL Synthetic 2-Stroke Injector Oil reduces wear and maximizes engine life. Its high lubricity and reliable film strength help protect against piston scuffing and bearing wear. Strenuous conditions define the normal operating environments of snowmobiles and boats. Without the right lubrication, two-stroke snowmobile engines and outboard motors... read more

Brand: AMSOIL • Product Code: AIO

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4-Stroke Synthetic Marine Oil

If you own a four-stroke engine, make sure the oil you use is formulated to withstand the increased stress of high-rpm operation. And use an oil designed to guard against rust and corrosion. Auto/light truck oils typically don’t contain sufficient rust and corrosion inhibitors for marine engines.

Formula 4-Stroke Marine 10W-40 Synthetic Motor Oil (WCF)

AMSOIL Formula 4-Stroke® Marine Synthetic Motor Oil is a premium-quality synthetic formulation engineered for the harsh operating conditions of marine environments. It withstands the intense mechanical action of continuous, high-rpm operation to deliver superior viscosity protection. Formula 4-Stroke Marine Synthetic Motor Oil is specially fortified... read more

Brand: AMSOIL • Product Code: WCF

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SAE 10W-30 Formula 4-Stroke® Marine Synthetic Motor Oil (WCT)

AMSOIL 10W-30 Formula 4-Stroke® Marine Synthetic Motor Oil (WCT) is a premium quality synthetic formulation engineered for the harsh operating conditions of marine environments. It withstands the intense mechanical action of continuous, high RPM operation to deliver superior viscosity protection. Formula 4-Stroke® Marine Synthetic Motor Oil... read more

Brand: AMSOIL • Product Code: WCT

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25W-40 Synthetic Blend Marine Engine Oil (WCM)

Protects Against Wear : Marine engines operate under high loads and rpm for extended periods. On average, a marine engine powering a boat 30 mph runs at about 5,000 rpm. In contrast, an automotive engine powering a car 60 mph runs at about 2,000 rpm. Higher stress causes traditional automotive oils to break down and lose viscosity. AMSOIL 25W-40... read more

Brand: AMSOIL • Product Code: WCM

25W-40 Synthetic Blend Marine Engine OilPricing Information or Place Order

Synthetic Heavy-Duty Diesel & Marine Motor Oil SAE 15W-40 (AME)

AMSOIL Synthetic Heavy Duty Diesel & Marine Motor Oil is a premium diesel oil that provides excellent performance in all types of diesel engines where highly effective control of wear and deposits is vital. Engineered with heavy-duty dispersant/detergent additives, its Total Base Number (TBN) of 12 neutralizes acids and controls soot thickening... read more

Brand: AMSOIL • Product Code: AME

Synthetic Heavy-Duty Diesel & Marine Motor Oil SAE 15W-40Pricing Information or Place Order

Synthetic Marine Gear Lube

Change lower unit gear lube – Your boat motor’s lower unit is continuously exposed to water. If water infiltrates the lower unit, the gear lube can foam, which compromises wear protection. Change the gear lube at the end of the season to ensure peak protection the following year.
Check the prop for debris – While you’re changing the gear lube, remove the prop and check for wrapped fishing line or other debris. It can damage the seal that keeps water out of the lower unit, allowing water intrusion.

75W/80W-90 Marine Gear Lube (AGM)

AMSOIL Universal Synthetic Marine Gear Lube is an exclusive AMSOIL formulation of synthetic base oils and high performance additives that address the specific concerns of marine applications. It is extreme pressure (EP) additive fortified for superior protection of fast accelerating, high torque/horsepower engines. It protects against shock loading... read more

Brand: AMSOIL • Product Code: AGM

75W/80W-90 Marine Gear Lube (AGM)Pricing Information or Place Order

Synthetic Grease

Grease trailer bearings – Like the tires, trailer wheel bearings are easy to overlook. They are submerged in water every time you launch and load your boat. Although the hub seals are designed to keep water out, age and neglect can allow water intrusion, which invites rust and corrosion. Rust acts like sandpaper and scours the ball bearings, causing them to run hotter and boil the grease out, worsening the problem. Grease the bearings at least once a year with a high-quality synthetic grease designed to resist water washout.
Grease tilt tube – Rust and corrosion can form on the tilt tube, preventing the motor from raising or lowering and restricting steering. At the end of the season, grease the tilt tube using a water-resistant grease. In addition to protecting against rust and corrosion, seasonal greasing also eases steering input.

Synthetic Water Resistant Grease (GWR)

AMSOIL Synthetic Water Resistant Grease is an extreme-pressure grease formulated specially for wet-duty performance. Composed of premium-quality synthetic base oils and calcium sulfonate complex thickeners, Water Resistant Grease provides exceptional film strength, shear resistance, adhesion properties and mechanical stability. Its water washout and... read more

Brand: AMSOIL • Product Code: GWR

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Fuel Additives

Treat fuel continuously during the season – Most people are accustomed to using automotive fuel additives periodically. In marine applications, however, it’s best to use them with every tank of fuel. Why? Because ethanol, present in most gasoline sold today, has a natural affinity for water. If moisture collects in your gas tank, it can bond with the ethanol and reduce performance. Treat fuel with an additive designed to keep water dispersed in the fuel tank and prevent phase separation, such as AMSOIL Quickshot®. Continuous use also helps prevent formation of performance-robbing deposits, varnish and gums.

Quickshot SE Additive & Stabilizer (AQS)

Degraded fuel presents a major maintenance issue in small engines and powersports equipment. It can form varnish, gum and insoluble debris that clog carburetors, fuel injectors and fuel filters. Carbon buildup can form on the tops of pistons that leads to pre-ignition, rough idling and poor throttle response. Fuel-related problems are only expected... read more

Brand: AMSOIL • Product Code: AQS

Quickshot SE Additive & Stabilizer (AQS)Pricing Information or Place Order

Gasoline Stabilizer (AST)

It is difficult to drain all of the fuel from equipment before storage, and doing so would expose the system to other problems, including the formation of rust and corrosion on the bare metal in the tank and fuel system and the drying and cracking of gaskets and seals. Some fuels are pre-treated with oxidation inhibitors that allow them to be stored.... read more

Brand: AMSOIL • Product Code: AST

Gasoline Stabilizer (AST)Pricing Information or Place Order

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Blog Title: AMSOIL Synthetic Lubricants for Marine Applications
Current Rating: 5 out of 5 stars
Votes & Reviews: 2 vote(s) and 2 user reviews.


Reviewed by RAPTOR 28: space

When Quality is all important

I run DOMINATOR 2-Stroke Racing Oil in my Raptor De 2 race car that is powered by a 494 rotax snow mobile motor. I never worry about problems evem in the heat of Florida or the severe stress running at Daytona Speedwlay. I have never had a problem and the motor always looks like new at rebuild time. Thanks Amsoil for a great product.

Item Reviewed: AMSOIL Synthetic Lubricants for Marine Applications
Discussion Url | New Port Richey, Florida

Reviewed by HITEKBALANCER: space

Evinrude ETEC XD100 replacement oil

I have been running HP marine in my Evinrude 300 on the lean oil setting for over two years. at least 300 hours of use. My dealer said the spark plugs look cleaner than most and almost did not need replacing after 300 hours. We opted to do so as we were going to put another 300 hours on it before the next service I burn 1/2 tp 3/4 of a gallon each day so XD 100 was adding up. I bought 3 cases of gallons when Amsoil offered free shipping. I was down aroind $30 per gallon where XD100 runs $44 to $48. at the local marina.

Item Reviewed: AMSOIL Synthetic Lubricants for Marine Applications
Discussion Url | Massachusetts,

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