Repair & maintenance guides

Boat Fuel Additives Explained: What Stabilizers, Ethanol Treatments and Boosters Really Do

The marine store shelf is full of bottles that promise to fix fuel problems. Learn what stabilizers, ethanol treatments, water removers, octane and cetane boosters, cleaners and diesel biocides actually do, what no additive can do, how to dose them by the label and why you should not stack several products in one tank.

Diesel Aftercooler (Charge-Air Cooler) Care: Why It Needs Service and Warning Signs

Many turbo diesels cool their intake air in an aftercooler with raw seawater running through it. If that cooler corrodes through, seawater can reach the cylinders and wreck the engine. Learn how to tell which type you have, the warning signs, the owner checks, and why the periodic removal and cleaning is a job for a pro.

Diesel Heat Exchanger Service: Zincs, End Caps, Tube Cleaning and Pressure Testing

Your diesel's heat exchanger moves engine heat into the seawater, and it slowly fills with scale, broken zinc pencils and impeller pieces. Learn how to check the zincs, open the end caps, clean the tubes safely, and when to have the core removed, descaled and pressure-tested by a shop.

Diesel Timing Belt: Does Your Engine Have One and When to Replace It

Find out whether your marine diesel's camshaft is driven by a rubber timing belt, a chain or gears, and if it is a belt, plan its replacement by hours and by age. A broken timing belt usually wrecks the engine and stops the boat on the spot, so this is one of the few jobs where "it seems fine" is not good enough.

Engine and Gearbox Oil Analysis: How to Take a Clean Sample and Read the Report

A lab oil analysis is like a blood test for your engine, transmission or lower unit. Learn how to pull a clean sample, what the lab measures, what wear metals, coolant, sea water and fuel in the oil can mean, and why the trend over several samples matters more than any one number.

Generator Pre-Trip Check: What to Inspect and Test Before a Cruise

A marine generator that quits on the first hot night of a cruise usually gave warning signs at the dock. Use this pre-departure checklist, based on generator makers' own advice, to inspect the oil, coolant, belt, raw-water side, exhaust and CO alarms, run the set under real load, and pack the right spares.

Gyro Stabilizer Care: Owner Checks for Seakeeper and Other Boat Gyros

A gyro stabilizer needs little from you, but what it needs matters. Learn how to start and shut it down correctly, keep its seawater cooling and zinc in shape, rinse it, read its hours and alarms, winterize it, and know which jobs belong to a certified dealer.

How to Break In a New or Rebuilt Boat Engine

The first hours on a new or rebuilt engine decide how well its piston rings seat and how long it lasts. Learn how to follow your maker's hour and RPM schedule, why you should keep changing the throttle, what to avoid (constant RPM, early full throttle, long idling), what to check every trip and when to do the first oil change.

How to Check and Change Coolant in a Closed Cooling System

Check, test and change the coolant in a freshwater-cooled (closed cooling) inboard, sterndrive or diesel, and learn the heat exchanger basics that keep it working. Old coolant quietly eats hoses, pumps and engine passages, and many boats go a decade without a change.

How to Check and Change Marine Transmission (Gearbox) Oil

Check, read and change the oil in the reverse gear behind your inboard diesel (ZF/Hurth, Kanzaki, Yanmar KM, Volvo Penta MS and similar). Learn what milky, burnt or gritty oil means, and why the oil cooler and its zinc matter.

How to Clean the Raw-Water Strainer and Replace the Impeller on a Marine Diesel

Clean the sea strainer and swap the rubber impeller in the raw-water pump of a Yanmar, Volvo Penta, Westerbeke, Beta or similar inboard diesel. A worn impeller is one of the most common reasons a diesel overheats, and this job takes about an hour with basic tools.

How to Deal with Diesel Fuel Contamination, Diesel Bug and Fuel Polishing

Learn the signs of water, sludge and microbial growth ("diesel bug") in your diesel tank, how to check a fuel sample, when a biocide helps, and when the tank needs polishing or cleaning. Clean fuel prevents most diesel breakdowns.

How to Find Your Engine's Serial Number, Model and Year (and Get the Official Manual)

Find the ID label on your outboard, sterndrive, inboard diesel or PWC, read the model and serial number correctly, tell it apart from the boat's HIN, and use it to open the free official owner's manual. It's the first step for ordering the right parts and following the right maintenance plan.

How to Get Better Fuel Economy From Your Boat

Boat fuel is expensive, but most owners can stretch every gallon further without buying anything. Learn how to find your boat's most efficient cruise RPM, why a clean bottom, the right prop, good trim and less weight matter most, which tune-up items count, how fuel flow data helps, and which fuel-saving myths to ignore.

How to Inspect and Clean a Raw-Water (Sea) Strainer

The sea strainer is the cheap screen that keeps weeds, shells and plastic out of your engine, generator and A/C pumps. Learn how to clean it safely with the seacock closed, reseal the lid so it can't suck air, spot a cracked bowl before it floods the boat, and winterize it.

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 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 Maintain Your Mainsail Reefing System and Practice a Reef at the Dock

Check the reef lines, blocks, hooks and cringles of a slab (jiffy) reefing system, keep in-mast and in-boom furling mains running smoothly, and practice tucking in a reef at the dock so it is quick and safe when the wind comes up.

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 Service Sailboat Winches (Clean, Oil the Pawls, Grease the Gears)

Take your sheet and halyard winches apart, clean out old grease and salt, oil the pawls, lightly grease the gears and bearings, and put them back together. A serviced winch turns easily and, more importantly, its pawls catch every time so the drum can't spin backward under load.

How to Synchronize Twin Engines (RPM and Trim)

Twin engines running at slightly different RPM cause a pulsing drone, extra vibration, uneven wear and wasted fuel. Learn how to sync them by tach, sync gauge or ear, use the one-button sync on digital controls, check that your tachs tell the truth, match trim, and know when uneven engines or cable adjustment are a dealer job.

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.

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.