Other than the required oil and lower unit fluid changes and other periodical maintenance steps outlined in your new four-stroke outboard owners manual, there are a few simple maintenance tips that can be done before and after each trip to ensure years of trouble-free use with your new outboard motor.
First and foremost you should ALWAYS flush the motor after use in salt water. Most new outboards have a built-in flusher where you can attach a hose and run fresh water through the interior engine cooling system. With some you can do this without having to run the motor and others require it to be running. Check your owner’s manual and make sure that you can run the motor while flushing. There are some manufacturers that state doing so can actually damage the engine. If an existing system is not present a simple “ear muff” flushing device can be placed over the water intakes on the lower unit and water is introduced through an attached garden hose. The motor is then started (and always run in neutral) and the water is circulated internally throughout the motor. This should be done long enough to thoroughly flush any salt out of the engine before storage. If one fails to flush the motor after each trip salt and corrosion can build up from the inside of the motor and lower unit and can cause damaging corrosion internally where it can’t be seen. The internal passages can also become clogged and overheating issues can result.
When you flush your motor you can see if the impeller that circulates the cooling water in the lower unit is working properly. Watching for a stream of water coming from just below the rear of the engine cowling when the engine is running will give you visual conformation. A strong steady stream indicates a healthy impeller. If there is just a trickle or nothing at all it may be time to replace an impeller (a simple job that can be performed by anyone who is moderately mechanically inclined). Failure to replace a worn or damaged impeller will lead to an overheated engine and a ruined day on the water.
Other simple preventative maintenance, including removing the cowling and spraying down the engine with a corrosion inhibitor such as Corrosion Block or T-9, will aid in fighting rust and corrosion in the hidden nooks and crannies of your motor. Greasing all grease fittings with a good specific purpose grease such as Mercury’s 2-4-C, which will not harden over time when exposed to salt water, will keep your motor moving freely. Also, putting a good coat of wax on your cowling to prevent sun and water fading will help prolong the shine and look of your motor. Checking engine and lower unit oil levels and topping up or changing if necessary helps the longevity of your new motor. If oil levels are excessively low or have a milky appearance it could be an indication of a possible problem and should be checked by a mechanic.
Another common maintenance task is to check fuel filters. Most motors will have an under cowl inline filter and a spin on gas-water separator. They should be checked regularly for water and other contaminants and changed as needed. Water and contaminants in the fuel are the single most common cause for marine engine trouble. This is especially true when using fuel containing ethanol and when the boat has sat unused for more than a couple of weeks.
Always adding a fuel additive each time you add fuel, such as those offered by Mercury, Yamaha, Startron, Sta-Bil and others, will help eliminate common fuel and ethanol issues and keep your fuel system clean and clear.
By following these and the other maintenance tips provided in your owner’s manual you are better assured of trouble-free time on the water and a long and happy relationship with your new motor.