Call us at 717-375-1025

Vanguard Big Block EFI Maintenance

Vanguard Big Block

When Argo was looking for a more powerful engine for their new Aurora line, there was only one place to turn: Briggs & Stratton. At 40 HP, their Vanguard Big Block EFI is as powerful as it gets in small engines. This marine engine also has a reputation for unfailing reliability, making it a great choice for the extreme locations Argos are used in. Here’s what you need to know to keep the engine in your Aurora 950 SX running smoothly.

Maintenance Schedule

To see the current hours on your machine, press the button on the right side of the gauge cluster until “HOURS” is displayed on the trip meter.

Every 100 hours or annually: Replace the spark plugs. Change the engine oil and filter. Service the air filter.
Every 250 hours: Have a mechanic check the valve clearance.
Every 400 hours or annually: Replace the air filter and fuel filter. Service the cooling system and clean the oil cooler fins.

Disconnect the spark plugs before working on your engine to prevent an accidental start.


Only use SAE-certified oil for gas engines in your Vanguard Big Block. Briggs & Stratton’s oil viscosity recommendations depend on ambient temperate. Choose the oil that best fits your operating conditions.

SAE 30: Between 40 and 100°F
10W-30: 0-100°F. Check the oil level frequently in hot weather. Oil consumption will increase above 80°F.
5W-30: Below 40°F
Synthetic 5W-30: Below 100°F
Vanguard Synthetic 15W-50: Above 20°F

When checking the oil, make sure the dipstick is fully inserted. If the oil level is too low, the engine’s ignition system will shut off automatically. When diagnosing a non-starting engine, this should be the first thing to check.

The engine’s position inside the hull makes it impossible to drain the oil from the engine using the drain plug. Instead, use a siphon pump to draw used oil through the dipstick tube.

To change the filter, first drain the oil. Unscrew the old filter. Apply a thin layer of clean oil to the new filter’s rubber gasket, then thread it onto the engine by hand. Once the filter seats, turn an additional ½ to ¾ turn to get a good seal.

The crankcase holds between 78 and 80 ounces of oil or about two-and-a-half quarts.

Air Filter

To access the filter elements, remove the thumb screw on top of the air filter box. Pull the cover off of the air box. Finally, unscrew the wing nut and lift the metal retainer off of the filter.

To clean the foam pre-filter, wash it in water and a mild detergent. Let it air dry. Do not oil this filter.

To clean the inner paper filter, tap it against a hard surface to dislodge dirt buildup.

Reassemble the air box in reverse order.

Fuel Filter

Before servicing the filter, drain the fuel tank.

Trace the fuel line from the air box until you see the filter. Use a pair of pliers to squeeze the tabs on the two clamps holding the fuel line onto the filter. Slide these clamps down the fuel line and away from the filter. Twist the lines to separate them from the filter’s inlet and outlet. Inspect the lines for signs of splits and leaks. Replace as needed.

Follow the previous instructions in reverse order to install the new filter. Be sure the arrow on the side of the filter is pointed toward the engine. Do not start the engine until any spilled fuel has evaporated.

Spark Plugs

The electrode gap should be 0.030 inches (0.76 mm.) When installing the plugs, torque them to 180 in-lbs.

Cooling System

To clean the cylinders, remove the air filter cover and unbolt the engine cover. Use a brush or dry cloth to wipe away dirt buildup on the cooling fins. Reinstall the covers. This same method can be used to clean the oil cooler. Do not spray the engine or cooler with water. Some of this water can make its way into the engine and contaminate the oil.

When You Need Help with Your Argo, Trust Shank’s Argo

If you’re looking to buy an amphibious ATV, or you need parts and service for your Argo, visit Shank’s Argo. We’re one of the largest dealers in the East, and we’re a certified Briggs & Stratton Vanguard dealer. Our shop is at 4900 Molly Pitcher Highway in Chambersburg, PA. That’s just one mile from Interstate 81.
To learn more, visit our website,

 , ,

Leave a Reply

Your email address will not be published. Required fields are marked *