Changing your oil at regular intervals is one of the best ways to extend the life of your engine. Old, dirty oil will not properly lubricate parts and will cause excess wear to your engine components. Fortunately, changing your oil is a relatively simple task that you can do yourself with a few tools.
How Often Should You Change Your Boat's Oil?
Engine manufacturers will usually list recommended service intervals in your owners manual which you should always use as your first source. If you do not have an owners manual or if there are no intervals listed in your manual, then changing your oil every 50–100 hours or once per year, whichever comes first, is a good rule of thumb.
How to Tell If it's Time to Change Your Boat's Oil
Even if you have not reached the recommended service interval, these warning signs indicate your engine oil should be changed soon:
- Oil appears dark, dirty, or milky
- Engine hours exceed manufacturer recommendations
- Boat has been idle for long periods
- Frequent short engine runs that do not reach full temperature
- Fuel smell present in the oil
- Evidence of water contamination
- Increased engine noise or rough operation
Tools & Products You Need to Change the Oil on Your Boat
- Correct marine engine oil meeting manufacturer specifications
- Replacement oil filter
- Oil extraction pump or drain system
- Oil absorbent pads or cloths
- Funnel for clean refilling
- Oil filter wrench
- Container for used oil
- Protective gloves and safety gear
How to Choose the Right Oil for Your Boat
Your engine manufacturer will list the recommended oil for your engine in your owners manual. Oil containers list the rating and viscosity of the oil on the front of the container so getting the right oil is as easy as matching what is in your manual to what is on the oil container when you go to buy.
Pay close attention to all letters and numbers listed in your owners manual as oil that is great for a gasoline engine may not work in a diesel engine and vice versa.
How to Change the Engine Oil On Your Boat
While changing the oil on your boat is more complicated than changing it on your car, with the right prep and the right tools you can make it as easy as possible. We'll walk your through it step by step.
Step 1: Run the Engine First
Warm oil is thinner so it is easier to withdraw through whatever method you use—especially if you’re using a dipstick tube. Plus, running the engine mixes all the gunk and contaminants into suspension, so you’ll be able to get all of the dirt out of the engine.
Step 2: Extract the Oil Using an Oil Change Pump
Most manual and electrical oil change pumps remove the oil from the engine using a skinny tube that feeds through the dipstick tube on your engine. Follow these steps to remove all oil from the engine.
- Remove dip stick, wipe it down and set it aside
- Feed the extraction tube down the dip stick tube as far as it will go
- Pump the oil out
- Pull the extraction tube out once all engine oil is removed and put the dipstick back in
Step 3: Change Your Oil Filter
You should always change your oil filter when changing the oil on your boat. Your oil filter will still have old oil it which will contaminate your fresh oil once it starts circulating.
- Remove the old oil filter. Make sure you have something underneath the oil filter to catch any oil in the filter that spills
- Lightly coat the gasket on the new oil filter with clean engine oil
- Hand tighten the filter on the engine giving it a three-quarter turn beyond the point where the seal makes contact with the flange.
Step 4: Refill Your Engine Oil
Refill your oil according to the engine manufacturer specifications. Owner's manuals usually specify the oil capacity, but you should check your oil level before running the engine to make sure the level is adequate. Make sure you have a funnel on hand as well to avoid spills when refilling.
Step 5: Run the Engine and Check Oil Level Again
Start your engine and let it get up to operating temperature then shut it off and wait 5-10 minutes before checking the oil level again to make sure it's correct. If it is low, top it off.
Bad spark plugs can cause a lot of problems for your boat including a drop in engine power, harder starts, reduced fuel efficiency and more. Luckily, changing your spark plugs is relatively simple and only requires a few hand tools that most DIYers already own.
Tools and Products You'll Need to Change the Spark Plugs on Your Boat
- A new set of spark plugs
- A ratchet
- An extension bar
- A spark plug socket that fits your spark plugs
How to Change Spark Plugs on a Boat
In this video, we change the spark plugs on a V6 outboard, but the process for changing the plugs on an inboard is generally the same
- Remove the spark plug wire making sure to number the plug wires if you are worried about mixing the wires up later
- Remove the old spark plug
- Check the gap on the new spark plug and set to the manufacturer's specifications if needed
- Install the new spark plug and torque to the manufacturers specifications
- Reattach the spark plug wire
- Repeat for all other spark plugs on the engine
Most sterndrive and outboard manufacturers advise you to change the gearcase oil in your lower unit every 100 hours or once a year (whichever comes first). Clean oil is critical for protecting the heavily loaded gears in your lower unit and preventing expensive damage. Servicing the lower unit is a simple job that you can easily do yourself.
What You'll Need to Change Your Lower Unit Oil
- A large, straight-blade screwdriver for the lower unit drain and vent plug screws
- Replacement O-rings/sealing washers for lower unit drain and vent plug screws
- Lower Unit Lube of the appropriate type
- Lower Unit Quart Pump & Lube Tube with an adapter fitting that fits your engine
- Catch pan for the used lower unit oil
- Container to carry used lower unit oil to a haz-mat recycling center
- Clean rags
- Disposable gloves, Mechanix Wear is a good bet
How to Change Your Lower Unit Oil
Step 1: The lower drain/fill plug screw is usually located on the starboard side of the lower unit, beneath the “bullet-shaped” portion of the lower unit housing. Locate your drain/fill plug screw and adjust the trim/tilt of your outboard motor or sterndrive so that this plug is in the lowest position possible in order to drain the used oil thoroughly.
Step 2: Use your large screwdriver to remove the lower drain plug screw. This is often easier said than done, because the steel screw in an aluminum housing can become stuck due to galvanic corrosion. If yours is stuck, try soaking the plug with penetrating oil, like WD-40, and letting it work overnight. You can also pick up a manual impact screwdriver (less than $10 at Harbor Freight) which turns the plug slightly when hit with a hammer. Finally, you can try using heat from a heat gun. Be patient and persistent, but try not to strip the slot in the plug head because drilling out the plug will be a major headache.
Step 3: With the drain plug screw loosened and your catch pan in place, keep pressure on the screw so it won’t fall into the pan and be covered with oil. Snatch it away as the oil begins to slowly drip out. Then remove the upper vent plug screw, usually located above the cavitation plate on the starboard side of the lower unit, and the oil will gush rapidly out of the drain hole. Give the oil plenty of time to drain completely, ideally for an hour or more.
Step 4: The lower drain plug screw often has a magnetic tip. Fine metal filings stuck there are normal, but you don’t want to see ‘chunks’ of metal. Inspect the oil in the pan. Again, you may see some sparkle of metal filings in the oil, which is normal. However, milky white or creamy colored oil indicates that water has contaminated the gearcase, and gray oil indicates some kind of failure in the gears or a bearing. Consult your mechanic if your lower unit shows any of the above danger signs. These need to be fixed before the boat goes back in the water.
Step 5: After the oil is completely drained, screw the oil pump adapter fitting to the lower drain hole, connect the Quart Pump which you’ve placed onto your quart of gear oil, and fill the lower unit. Keep pumping until the oil runs out the upper vent plug hole indicating the oil level is high enough.
Step 6: We recommend installing new O-rings/sealing washers on your drain and vent plug screws and coating them with a little non-metallic, marine-grade anti-seize compound to make them easier to remove in the future. Clean all the metal flakes from the tip of both plug screws, and replace the upper vent plug screw in the lower unit. Next, you’ll remove the oil pump adapter fitting from the lower drain hole, with the lower drain screw in your hand and ready. Quickly replace the screw so only a little oil runs out.
Step 7: Now you can thoroughly wipe the exterior of your lower unit to keep the oil out of the environment. Then bottle up the used oil and take it to the local recycling center.
Inboard and sterndrive engines usually include a flexible impeller type raw water pump. You should check the impeller’s condition during winterization and every 200 hours of operation. We also recommend carrying a spare on your boat in case it fails while your on the water, leaving you stranded in the process.
How to Change the Impeller on Your Boat
Step 1:
Close the thru-hull
Step 2:
Remove the three to six end cover screws and remove the cover and gasket
Step 3:
Remove the old impeller by gripping the hub of the impeller using channel lock or needle-nosed pliers, or an impeller puller tool.
NOTE: Do not use a screwdriver to lever out the impeller. The screwdriver can score the soft bronze body of the pump and cause leaks.
Step 4:
Examine the impeller once it's out of the pump. The tips of the vanes should be round, not flat, and there should be no cracked vanes or distortion in their shape. Check each vane by bending it.
If the impeller is in pieces, be sure to get all the bits out and be sure they are all accounted for. Little chunks of rubber can migrate into the heat exchanger or the engine and cause overheating damage.
Step 5:
Lightly lubricate the inside of the impeller housing with Vaseline to reduce the friction of the first dry startup. Use a heavy rubber band or loop of light line to collapse the impeller’s vanes, insert it, and pull the loop our with your pliers.
Step 6:
Replace the cover and reinstall the screws.