How to Keep Your Marine Motor Running Well Long-Term

Pat Burgraff, an AMSOIL Mechanical Lab Technician, has 25 years of experience working with marine motors. Pat has worked on almost every make and model of inboard and outboard motors on the water today. In this time, he has learned firsthand the issues that motors can have and what is necessary to make sure enthusiasts receive the maximum amount of years and performance from their motors.

Here are Pat’s tips to ensure your marine motor continues to run efficiently for years:

1. Use your motor

One of the best ways to make sure your motor is running well is to consistently use it. Gasoline begins breaking down in as little as 30 days. Assorted debris, varnish, and gums can plug the small fuel channels in the carburetor, which prohibits the motor from running or even starting properly. “The carburetor can plug up pretty quickly and easily,” said Burgraff, “especially on smaller four-stroke motors.” 

After 25 years of experience, Burgraff said compromised gasoline is one of the leading causes of marine motor issues. Keeping the gasoline in your boat and motor in use will help keep the fuel system running efficiently and keep it clean. Using your boat also conditions seals and gaskets, keeping them safe from leaking and/or drying out.

2. Keep the gas stable

As much as we’d like to, we can’t always make time to fish or boat. If you find yourself not able to hit the water as often as you want, be sure you stabilize your boat fuel to keep it from oxidizing and disintegrating. We recommend even making a habit of adding stabilizer each time you fill your gas tank. AMSOIL Gasoline Stabilizer helps protect fuel during long-term storage and encourages fuel freshness for up to a year, while also fighting corrosion.

If you are storing your boat for fewer than six months or actively using your boat, AMSOIL Quickshot® offers a great solution. Not only does it keep your fuel stable, but it also works to clean components and fight ethanol-related effects.

3. Keep gas cans and tanks covered

Water is responsible for several fuel problems. Keep gas tanks and gas cans covered to keep water out.  “If you leave your gas can uncovered in the rain, water can enter through the vent cap and contaminate the gas,” said Burgraff. 

If water gets into the combustion chamber, this can cause serious damage to your engine. Water can also build up and cause a plug in the fuel system, resulting in the motor running rough, or keeping it from starting at all. Ethanol in fuel can absorb the water and create a separation of water/ethanol and gasoline that will fall to the bottom of the tank, causing what is referred to as phase separation.

AMSOIL Quickshot assists in keeping water moving throughout the fuel and helps move it through the combustion chamber normally and keeps it in good working order. 

4. Make sure tilt lube and steering are greased

Another issue attributed to water is getting into the tilt lube and creating corrosion. This keeps you from being able to easily lower or raise the motor. “A lot of people forget to grease the tilt tube and steering,” said Burgraff. “Don’t overlook this step, or it’s only a matter of time before corrosion forms.” AMSOIL Synthetic Water-Resistant Grease is ideal for helping prevent corrosion in tilt lubes and steering. It sticks well to metal and prevents water washout to stay in its place, protecting the material and resisting rust.

5. Switch out lower-unit gear lube

Water can get into the lower unit and pollute the gear lube, which diminishes its ability to defend against wear. Gear lube that has been polluted with water can also create foam, and when bubbles get between gear teeth, it creates a collapse of the bubble and leads to metal wear. In order to keep gear lube in good condition over the winter, be sure to change your gear lube before storage in the autumn to get rid of water. The AMSOIL Synthetic Marine Gear Lube makes changing your gear lube simple and negates the need to use a messy lubricant pump.

6. Don’t forget to grease bearings on trailers

Many often neglect to grease trailer bearings, the grease of which can be negatively impacted by exposure to water. “A couple times a year, pump a little grease in the bearings to push out any water that may have accumulated,” said Burgraff.

AMSOIL Synthetic Water-Resistant Grease is ideal for greasing trailer bearings. The grease resists rust formation and helps to keep your trailer on the road.

7. Keep up with oil level and condition of four-stroke motors

Gasoline can get into the oil sump in four-stroke motors, tainting the oil. This is referred to as fuel dilution. If the motor does not get to normal temperature of operation, the fuel will not burn well, which leads to fuel getting past the piston rings and into the oil sump. Ideally, the oil should get to a high enough temperature to evaporate fuel that has amassed.

“On a cold body of water, however, the engine may not get hot enough to evaporate fuel in the oil,” said Burgraff. “If you notice the oil level has increased and oil color is normal, you may have fuel in the oil.” 

Unfortunately, fuel dilution decreases the viscosity of the oil, decreasing protection from wear. Fuel dilution also leads to quicker oil breakdown, which means more oil change. Change the oil and be sure to run the engine for long enough that it reaches ideal operating temperature on occasion—this will help prevent the issue in the future. If the level of oil is higher, but the color and consistency looks milky, there’s a good chance you have water in the oil, caused by a defective head gasket. If this happens, stop running the motor until it can be repaired.