Attention Boaters: This is a MUST-HAVE Outboard Motor Maintenance Checklist

Attention Boaters: This is a MUST-HAVE Outboard Motor Maintenance Checklist

October 22, 2021

Boat ownership will often take some work, but the experience is always better when you have tools and resources to eliminate frustration. That's why we're sharing some quick-links to commonly-needed products along with a must-have seasonal outboard motor maintenance checklist — and you can find it all right here!

Tools and Tips for Easier Seasonal Outboard Motor Maintenance

When you think about what it takes to maintain your boat and outboard motor with each outing and each season, keep in mind that there are many tools and pieces of equipment designed to make it all go smoother. From seasonal outboard motor maintenance to other related tips, here is our list of highly-recommended tools, equipment, and advice to go along with the incredibly easy-to-use checklist located at the bottom of this post.

Checklist Highlight #1: Getting a Look at Your Propeller and Skeg

MUST-HAVE Outboard Motor Maintenance ChecklistWhether you're pretty sure you haven't run aground with your propeller or you suspect that it's possible (shout out to all of you sharing the wheel with others), it's crucial to check the condition of your propeller regularly. If your boat is running slow, running inefficiently, or if your propeller has visible warping / notching, it might be time to change your propeller.

To make that propeller change easier, consider the Prop Master Prop Wrench and the Prop Master Propeller Stop. (The Prop Spot may also help if you need somewhere to store your propeller). As the original molded propeller wrench, the Prop Master Prop Wrench is designed with high tensile strength, indestructible nylon that is resistant to fuel, sun, salt water, and other chemicals. That design also makes it less expensive and less likely to rattle and cause damage when stowed. The Prop Wrench works even better when you have the Prop Stop in place on the outboard motor's anti-cavitation plate, stopping the propeller from moving while you loosen the propeller nut.

TH Marine Gear Prop Master Propeller Wrench
T-H Marine Supplies Prop Master Prop Stop Propeller Stop
TH Marine Gear Prop Spot - Spare Prop Retainer for Boats


While looking at the propeller, take a look at your skeg, for signs of wear, too. The skeg may look quite low-key, but, as the lowest point on an outboard motor, it acts as a rudder and helps keep the propeller from getting caught on submerged objects. When the skeg wears down or incurs damage, it compromises your ability to steer and your ability to protect your propeller.

Checklist Highlight #2: Minding Your Outboard Mounting Hardware, Jack Plate, and Hydraulics

A certified marine mechanic is your safest bet for using manufacturer's specifications to check mounting bolts on your transom and jack plate, but it doesn't hurt to take a preliminary look for obvious signs of needed maintenance. Thankfully, jack plates are designed to be low maintenance, but it's better to be sure and have peace of mind, especially with pricey outboards attached to them.

Start by looking for visible signs of wear or looseness with mounting hardware on your transom and where the jack plate mounts to the outboard. Additionally, test your tilt and trim to make sure you have responsiveness and smooth operation (and do the same with your hydraulic jack plate if you have one).

If you have an Atlas Hydraulic Jack Plate from T-H Marine, it usually doesn't take much to make sure it's running properly, but if it seems like it needs some attention to make it run smoothly, maintenance is likely as easy as cleaning the hydraulic rods with dish detergent (no lubricant needed!).

Checklist Highlight #3: Flush your Engine

For optimal performance and long life for your outboard, you should flush your engine after every outing if you're running your boat in saltwater and flush it about every 2 or 3 outings if you are running your boat in freshwater. This will help wash out salt, sand, silt, alkali, and mud, keep deposits from gathering in the lower unit, and prevent corrosion and damage to the water pump impeller.

There are two main methods to flushing out a motor. For the first that we'll highlight, look at your outboard to see if it has a built-in flushing port. If it does, this flushing port provides a threaded connection where you will attach a garden hose connected to a fresh water supply. IMPORTANT NOTE: Before going any further with this method, please note that you should NOT run the engine while you are flushing it out this way.

As shown in the video above, use the threading on your outboard flushing port to attach a garden hose. If you don't see a flushing port, skip to the second method detailed below. Since this process should be performed regularly, consider adding a Quick Flush Fitting like the one pictured here. This fitting makes flushing the outboard quick and easy, with no need to strain your fingers twisting the hose connector over a threaded fitting.

Once you've connected the hose to your outboard, either using the threaded port or the aftermarket quick connect linked above, be sure to flush it out for at least 5 minutes. If you flush the engine for at least 5 minutes, that should allow enough time to dissolve salt crystals and deposits that may be inside. If your boat stays in a slip, you will want to tilt the engine up during this process to make sure you're completely flushing it out.

If your outboard does not have a built-in hose connection, which is common for older outboards, you will need to use something commonly referred to as "earmuffs" or an outboard motor flusher.

T-H Marine Supplies Large PVC Motor Flusher
First Source Universal Motor Flush
First Source Dual Flow Motor Flusher

This will also use a hose with one end connected to a fresh water supply, but the other end of the hose will be connected to the threaded receiver portion of the motor flusher (pictured above). This type of motor flusher is designed to attach to the lower unit of the outboard and the "earmuffs" on it slide over the water intakes, so you will need to make sure they are completely secured over them for this flushing method to work.

Once the motor flusher is secure over the intakes, start the hose water and look at both sides of the earmuffs to make sure there is water flowing through the intakes. To complete the process, the earmuffs method will require starting the engine, so safely start your outboard, use all necessary precautions, make sure the earmuffs don't vibrate off of the intakes, and make sure that the engine is pushing the water back out. This final part tells you that it has a good supply flushing it out.

The system should be adequately flushed after running it for 5 minutes.

Checklist Highlight #4: Inspecting Your Fuel Line and Fuel Line Components

If your fuel line doesn't seem to build pressure when you squeeze the primer bulb, if you see evidence of fuel leaking, if you suspect air or contaminants are getting in, or the line is otherwise not delivering fuel efficiently, your motor isn't going to work consistently like it should. Buying ethanol-free fuel, using a marine fuel additive, and servicing your engine can help quite a bit to keep that outboard reliable, but don't neglect easy factors like updating the fuel line that runs from your gas tank to your outboard.

T-H Marine Supplies Yamaha Fuel Connector
First Source Universal Fuel line Assembly
First Source Mercury Fuel Line Assembly

Over time, connectors can wear out on either side of the fuel line, the hose line itself can develop weaknesses and cracks, and primer bulbs wear out. The good news is that some fuel line components are under $5, entire fuel lines are typically under $50, and each of them can usually be serviced in 15 minutes or less.

Checklist Highlight #5: Replacing Fuel Filters / Water Separators

You need to replace your fuel filters / water separators when you reach 100 hours on your outboard. This really does mean replace, too, because you definitely should not just dump it out and reinstall it. Dumping it out and reinstalling it will lead to a contamination of your fuel system and that will lead to engine failure.

For the best, manufacturer-specific advice about how to replace your fuel filter / water separators, consult your owners manual.

Checklist Highlight #6: Monitoring Oil and Replenishing Oil

Fair warning here that the process can vary substantially from outboard to outboard, so this checklist item may involve a learning curve, especially if you've never opened the cowl of your outboard before. The bottom line, however, is making sure you have the proper lubrication to keep your engine working, whether that's learning how to properly do it yourself or contacting a local marine mechanic.

If you're interested in learning to take your DIYing to this level, be sure to consult your owners manual and How-To Videos like this one from BoatUS and consider tools and equipment that make it easier like the manual oil changer kit and 12 volt oil changer shown below.

T-H Marine Supplies Oil Changer / Fluid Evacuator Kit
T-H Marine Supplies 12 Volt Oil Changer
Checklist Highlight #7: Review Your Trailering Equipment

For our last highlight before we get to the checklist below, review your trailering equipment so you have an operable and optimal setup that protects your outboard and keeps you ready for the road.

Focusing specifically on components that help secure your outboard while it's out of the water, routinely check the condition of your transom tie-down straps and employ the use of outboard trailering equipment like transom brackets, outboard motor supports, and outboard hydraulic steering locks. These keep your outboard from bumping around and getting damaged during transport.

First Source Transom Tie-Down Straps

Transom Tie-Down Straps

T-H Marine Supplies 26

Transom Brackets

TH Marine Gear Motor Stik OutBoard Motor Support Stick Pair

Outboard Motor Supports

TH Marine Gear 4

Outboard Steering Locks

Save This Must-Have Outboard Motor Maintenance Checklist ⬇️

For a more extensive outboard motor maintenance checklist, courtesy of our friends at BoatingUS, refer to the guide below or download the full boat maintenance checklist using the button below.

General Guidance Below. Always consult your user manual for model-specific instructions. Every Outing Every 20 hrs. Every 50 hrs. Every 100 hrs. Before Layup Video
Engine and Drive
Check oil/fill View
Check transom mounting bolts/jack plate bolts (if equipped)  
Check propeller and skeg for damage View
Check cowl air intakes for blockages  
Check engine operating temperature  
Check oil pressure  
Check drive/gearcase for water/particulate/burnt lubricant & refill    
Check engine for proper operating RPM @ WOT    
Check fuel lines for alcohol and UV degradation      
Replace fuel/water separating filter      
Check power trim/tilt fluid, refill if necessary      
Check engine mounts and swivel/steering bracket for excessive play      
Lubricate all grease points        
Coat electrical w/silicone protectant spray        
Have linkage/synchronization checked        
Retorque all accessible bolts/fasteners        
Touch up paint        
Check spark plugs and replace as necessary          
Change and check condition of gearcase lube and powerhead oil         View
Replace water-pump impeller          
Treat fuel with storage conditioner, fog engine, drain/refill oil, replace oil/fuel filters          
Steering System View
Check for excessive play/movement  
Check fluid level/check for leaks/bleed system (hydraulic)      
Check engine free-play and adjust      
Lubricate all grease points      
Check for kinks (hydraulic and mechanical) and/or binding (mechanical)