Extend the Life of Your Outboard Engines: Suggested Preventative Maintenance Tips and Techniques

Here are some helpful engine maintenance instructions and tips for sailors and boaters…

1. Spark Plugs
There is one spark plug per cylinder, typically located near the aft end of the engine. On older 2-stroke models, they are usually easy to access. Some of the larger 4-strokes have sacrificed ease of access for space saving which sometimes makes it very frustrating to reach them. Somewhere on the engine will be a sticker that indicates what type of spark plug the engine uses as well as the gap setting. It is very important that you follow these specifications.

After removing the old spark plugs, adjust the gap on the new plugs to the proper specification and hand tighten into the holes. Use a torque wrench to tighten to approximately 15 foot pounds. If you do not have a torque wrench, hand-tighten as much as you can and then you a socket wrench to ‘snug’ it a bit. DO NOT overtighten as this can crack the plug or cause damage to the cylinder.

Suggested tools – socket set, articulating socket wrench, socket extension, torque wrench (in inch pounds), spark gap tool.

Pro tip: Make sure to hand thread first the plug first, then use the wrench otherwise you run the risk of crossthreading.


2. Oil & Filter
2-strokes will not have an oil filter and depending on the kind, will either take a gas/oil mix, or if it is a direct injection, will have an oil reservoir that needs to be periodically checked and filled. 4-strokes will have an oil filter that gets changed when you change the oil. There are two ways to drain the oil out of a 4-stroke – either through the drain plug on the outdrive, or by inserting a tube into the dipstick hole and pumping the oil out. In either case, make sure that the engine has been warmed up to at least 60° so that the oil will be less viscous and will drain more effectively.

When replacing the filter, it doesn’t hurt to pre-fill it a bit (not so much that it spills) and be sure to lubricate the gasket before reattaching it to the engine. As with the spark plugs, hand-tighten it first, then use the torque wrench to tighten to about 15 foot pounds. Make sure to mark the date on the filter so that you know when it was changed.

Suggested tools – oil filter wrench/cap, socket wrench / torque wrench, swivel band grip, oil pump with reservoir (if removing through dipstick hole), screwdriver, oil container, paper towels, fresh oil.

Pro tip: Whenever adding oil, it is extremely important that the engine is as level as you can get it and you have allowed the oil to settle – otherwise the reading on the dip stick will not be accurate. Our mechanic strongly recommends sticking with the engine manufacturer’s brand of oil filter to avoid any size or performance issues.


3. Lower Unit
The lower unit has two fill holes that allow for draining and refilling of the gear oil.


4. Oil & Gaskets
These screws are typically magnetic and will attract and hold any stray metal shavings that have come off the gears. They will also have a gasket around them made of either a papery material or of rubber wrapped metal. To drain the oil, first remove the lower screw, then remove the top. Inspect the oil for any signs of water and clean the screws. It is recommended that you replace the gaskets every time you change the oil.

Once the oil has fully drained, attach the oil pump at the BOTTOM hole and pump until you see oil coming out of the top hole. When you are sure that the case is full, screw the top screw and gasket back in. Detach the oil pump and replace the lower screw and gasket.

Suggested tools – flathead screwdriver, plastic paint tray liner or something of the equivalent to catch the oil, new gaskets, oil w/pump, pump adapter (if necessary), paper towels.

Pro tip: NEVER replace a screw without a gasket (especially the top screw). It will end very badly as all the oil slowly drains out and is replaced by water. Sometimes the gaskets will stick to the engine and not the screw when it was removed – make sure you check this!**


5. Grease Points
There are several grease points located on an outboard engine. They will vary depending on the make of your engine but in general, there will be 2-3 ‘nipple’ attachments located near the engine mount. These points will lubricate the up and down motion of the engine, the side to side motion, and the steering cable. Use waterproof marine grease and a grease gun to lubricate these points (same thing you use on your trailers).

You will also want to lubricate any other moving parts of the engine including the throttle linkage, cowling latch, and various pivot points to name a few. You can use the same waterproof grease applied manually or a spray such as Boeshield or the equivalent.

Suggested tools – grease + grease gun w/attachment, Boeshield, paper towels.


6. Fuel Filters
If you have an external filter on your boat, unscrew the old filter and replace with a new one.

The internal fuel filter will be located near the fuel pump and will be a clear plastic container with a filter element inside. Consult your engine’s manual for the correct way to remove it.

Once removed, clean out any residue and replace the filter.

Suggested tools – ziplock bags (to contain the filters), swivel band grip, adjustable wrench.


7. Batteries
If you can, remove your batteries at the end of the season and store them in a temperature controlled location. If you do not have this option, make sure that your battery is charged before letting it sit through the cold winter months. A discharged battery runs the risk of freezing and cracking in cold temperatures.

Make sure to routinely clean your battery terminals with a wire brush and coat the terminals and connections with a dielectric grease or petroleum jelly to prevent corrosion.

If you have an unsealed, flooded battery you will need to periodically open the caps and top of the water inside. This should be done before charging the battery to capacity.


Lynn Lynch
Race Manager
St. Francis Yacht Club