Repair & maintenance guides

How to Inspect and Replace Exhaust Shutters and Flapper Valves

The rubber shutters inside a sterndrive's exhaust and the flappers at an inboard's exhaust outlet are one-way valves that keep water from washing back into the engine. Learn where they are, how they fail, how to check them every year, and why riser service is the perfect time to replace them.

How to Inspect and Replace Sacrificial Anodes (Zincs)

Check the anodes on your outboard, sterndrive or inboard running gear, replace them when they are half gone, and choose the right metal for the water you boat in. Fresh anodes are cheap insurance against expensive corrosion damage to your lower unit, drive and prop.

How to Inspect and Replace Spark Plugs

Pull, read and replace the spark plugs on a gas outboard, sterndrive, inboard or PWC. Fresh, correctly gapped plugs help the engine start easily and run smoothly, and the old plugs tell you a lot about the engine's health.

How to Inspect Engine Belts and the Tensioner on Sterndrives, Inboards and Diesels

On many inboard, sterndrive and diesel engines, one belt runs the water pump, the alternator and often the power steering. If it breaks or jumps off, the engine overheats and the steering goes heavy at the same moment. Learn how to inspect the belt, tensioner and pulleys, check tension, and carry the right spare.

How to Keep a Boat Maintenance Log and Organize Your Receipts

Set up a simple maintenance log that records the date, engine hours, work done, parts and who did it, and keep receipts and photos organized. Good records help with warranty and insurance claims, show buyers the boat was cared for and reveal wear patterns before something fails.

How to Remove and Reinstall an Outboard Gearcase (Lower Unit) Without Losing Shift

Dropping the lower unit is the first step of every outboard water pump job, and the reinstall is where most DIY trouble starts: no forward gear, no cooling water or a driveshaft that will not seat. Learn how to set the shift position, protect the water tube, line up the splines and test everything before the boat goes back in the water.

How to Replace a Fuel/Water Separating Filter (and Check for Water in Your Fuel)

Swap the spin-on fuel/water separator on your gas boat and learn to spot water and ethanol phase separation before it stalls the engine. It is one of the cheapest jobs on the boat and one of the best protections for a fuel-injected engine.

How to Replace an Outboard Fuel Line and Primer Bulb

A cracked hose or a stiff primer bulb can leak gasoline, starve your engine or shed rubber into the fuel. Learn how to choose Coast Guard-rated fuel hose, the right connectors for your engine brand and good stainless clamps, install the bulb pointing the right way, leak-test the job and get rid of the old parts safely.

How to Replace the Water Pump Impeller

Replace the rubber impeller that pumps cooling water through your engine, the part most often behind overheating. On many outboards it is a two-hour driveway job that saves a shop bill of several hundred dollars and prevents far costlier heat damage.

How to Sea Trial Your Boat After Maintenance or Repair

A step-by-step test run after service work: dock checks first (leaks, fluids, steering, kill switch), then a gradual climb through the RPM range while you watch temperature and pressure, a wide-open-throttle check against your engine's spec, shifting and trim tests, and a bilge check afterward. Catch a loose clamp or a missed step at the dock, not miles out.

How to Test and Replace the Engine Thermostat

Find, test and replace the thermostat that controls your engine's operating temperature. A stuck thermostat can make an engine overheat or run too cold. On most outboards and many sterndrives it is a one-hour job with basic tools.

How to Use an Oil Extractor Pump for Boat Oil Changes

Change engine oil cleanly through the dipstick tube with a manual or electric extractor: know which engines it suits, warm the oil first, get as much out as you can, then refill to the dipstick, recycle the old oil and clean the pump so it's ready next time.

Jet Outboard Care: Grease, Intake Grate, Impeller Clearance and Shallow-River Habits

A jet outboard trades the propeller and gearcase for a pump, so it needs different care. Learn how mounting height works, why the pump bearing needs frequent grease, how gravel and a worn impeller steal thrust, how to clear the intake safely, and when an adjustment is a shop job.

Marine Diesel Service: Oil Change, Fuel Filters and Bleeding Air

Change the oil and oil filter, replace the primary and secondary fuel filters, and bleed air from the fuel system on a Yanmar, Volvo Penta, Beta, Cummins or similar marine diesel. These three skills cover most routine diesel care and can get you out of trouble when the engine dies on a passage.

Marine Diesel Turbocharger Care: Warm-Up, Cool-Down and Simple Checks

A turbocharger needs little attention, but the attention it needs matters. Learn how to warm up and cool down a turbo diesel, keep its oil and air clean, track boost, spot leaks and salt corrosion early, and know when a turbo needs a professional.

Moving Your Boat From Fresh to Salt Water (or Back): Anodes, Flushing, Corrosion, Bottom Paint and Trailer Upgrades

What to change when a lake boat moves to the coast, or a saltwater boat moves inland: switching anode material, a flush-after-every-trip routine, raw-water and closed cooling parts that wear faster in salt, bottom paint that suits your hull and drive, marine-grade hardware, and trailer upgrades that survive salt dunks. Built from BoatUS, Mercury, Yamaha and Boating Magazine advice.

Onboard Tool Kit and Spare Parts: What to Carry on a Day Boat or a Cruiser

Build a tool kit and spares box that fits your boat and how far you go. A blown fuse, a clogged fuel filter or a dinged prop shouldn't end the day or turn into an expensive tow.

Portable Toilets on Boats: Emptying, Chemicals, Odor, Seals and Winter Storage

A portable toilet (Porta Potti type) is the simplest legal head for a small boat, as long as it is emptied the right way. Learn where to dump it, which chemicals to use, how to stop odor and leaks, how to secure it aboard, and how to store it for winter.

Propeller Care: Inspect, Remove, Replace and Choose the Right Pitch

Check your prop for damage, pull it to clear fishing line and grease the shaft, reinstall it correctly, and learn how pitch affects your engine's wide-open-throttle RPM. The right prop in good shape protects your engine and often makes the boat run better and use less fuel.

Salt and Scale in Raw-Water Cooling: Flushing Habits, Descaling and When It's a Shop Job

Learn how salt and scale slowly narrow your engine's cooling passages, how to spot the warning signs (a temperature that creeps up over seasons, a weak telltale, thermostats sticking), the flushing habits that prevent it, which descaling products and methods engine makers accept, what never to pour through an engine, and when to hand the job to a shop.

Saltwater Outboard Care: The After-Every-Trip and Monthly Routine

A simple routine that keeps salt from eating your outboard, built from Honda, Yamaha, Mercury and Suzuki advice. It covers flushing after every trip, washing, where to spray anticorrosion (and where never to), monthly greasing, anodes, and tilting up or storing out of the water.

Small Portable Outboard Care (2.5 to 20 hp Kickers and Dinghy Motors)

Keep your dinghy motor or kicker starting on the first few pulls. Use fresh fuel, flush it, run the carburetor dry before you put it away, carry and lay it down on the correct side so oil doesn't flood the cylinders, and check the shear pin or prop, gear oil and engine oil on schedule.

Testing Engine Coolant: Test Strips, Refractometer or Lab Analysis

Coolant can look perfect and still be worn out. Learn how to test the coolant in a closed-cooled inboard, sterndrive, diesel or generator with test strips, a refractometer or a mail-in lab kit, what each result tells you, and when the answer is a coolant change or a call to a mechanic.

Two-Stroke Oil Injection vs. Premix: How It Works and How to Check It

A two-stroke engine dies quickly without oil in its fuel, so the oil injection system and its alarms deserve regular attention. Learn how injection and premix differ, what the warning horn is telling you, how to check the system, how to premix safely using your manual's ratio, and the real risks of disabling injection.