Repair & maintenance guides

Boat Slower Than It Used to Be? How to Find the Cause

When your boat loses top speed or takes longer to get on plane, the cause is usually something you can check yourself: extra weight, water in the hull, trim, a dinged or fouled prop, or a dirty bottom. This step-by-step diagnosis goes from the cheapest checks to the harder ones and explains what your RPM and GPS speed are telling you.

Boat Speedometer Reads Zero or Wrong: Pitot Pickups, Paddlewheels and GPS Speed

Fix a speedometer that reads zero, too low or jumps around. Learn which kind you have, clear a clogged pitot pickup and hose, clean and calibrate a paddlewheel, check the speed source on digital gauges, and decide whether switching to a GPS speedometer makes sense.

Diesel Exhaust Smoke: What Black, White and Blue Smoke Mean

Learn to read the color of your marine diesel's exhaust and run the simple checks that go with each color, from a dirty air filter or fouled prop to a worn mixing elbow or head gasket. Catching smoke early can save an engine.

Diesel Fuel Injectors: Symptoms, Checks and When to Send Them Out

Learn the signs of a failing diesel injector (smoke, rough idle, hard starting, knocking), how to rule out the cheaper causes first, why testing and rebuilding injectors is a job for a fuel-injection shop, and how clean, dry, well-filtered fuel keeps them healthy.

EFI Outboard Cranks but Won't Start, No Key-On Beep or Fuel Pump Hum

When a fuel-injected outboard turns over but stays silent at key-on (no warning-horn chirp, no fuel pump priming), the engine computer usually isn't waking up. Work through the lanyard, battery voltage while cranking, main fuses, relays, harness plugs and grounds before anyone blames the computer.

EFI Outboard Vapor Separator Tank (VST) and Injectors - Symptoms, Filters and When It's a Dealer Job

On a fuel-injected outboard, the vapor separator tank holds fuel right at the engine and feeds the high-pressure pump and injectors. Learn why ethanol varnish and debris clog its filter, how a starving VST feels (stalls at speed, won't hold RPM), what you can safely maintain yourself, and when it's time for the dealer.

Electric Marine Toilet Troubleshooting: Won't Flush, Weak Flush, Won't Stop Filling

Electric and macerating marine heads fail in a handful of predictable ways. Work from the cheapest checks to the messiest ones to fix a toilet that won't run, flushes weakly, trips its breaker, keeps filling, loses or gains water in the bowl, or backs up, and learn what to keep out of it.

Engine Overheating - Troubleshooting Guide

Work through the most likely causes of a hot engine or overheat alarm, from a blocked water intake to a worn impeller or stuck thermostat. Acting fast and in the right order can save your engine and often gets you home without a tow.

Engine Starts Then Dies - Troubleshooting Guide

Track down why your boat engine fires up and then stalls, whether at idle, when you shift into gear, or after a few minutes of running. Most causes are in the fuel supply and can be checked with no special tools.

Engine Warning Horn and Dash Lights: What They Usually Mean and What to Do

Learn what a warning horn, beeps or a dash light usually mean on a boat engine, from overheating and low oil pressure to water in the fuel and reduced-power (limp) mode. Find out what to do right away and when to stop the engine. Patterns differ by brand, so match what you hear and see to your owner's manual.

Engine Won't Start or Won't Crank - Troubleshooting Guide

Find out why your boat engine will not turn over or will not fire, starting with the simple things owners miss most, like the kill switch lanyard and battery switch. Many no-starts are fixed at the ramp in minutes without a tow.

Four-Stroke Outboard Oil Level Rising or Smelling Like Gas: What It Means and What to Do

If the oil on your four-stroke outboard's dipstick keeps going up or smells like gasoline, fuel is probably getting into the crankcase. Learn how to check the level the right way, why lots of idling, trolling, short runs and cold water cause it, what you can do yourself, and when a fuel-system fault needs a dealer.

Freshwater Pump Troubleshooting: Cycling, Won't Shut Off or No Water

When the pressure water pump keeps cycling at night, runs nonstop or sputters air, the cause is usually simple: an empty tank, a dripping fixture, a clogged strainer, air in the lines or a tired accumulator. Work from the cheapest checks to the pressure switch and pump, and learn the basics of replacing a pump.

Fuel Anti-Siphon Valve: Diagnosing a Sticking Valve and Replacing It Safely

The anti-siphon valve at your built-in fuel tank stops gasoline from draining into the bilge if a fuel line breaks, but a cheap or sticky one can starve the engine at speed. Learn how to tell a restricted valve from a blocked vent or filter, how to clean or replace it with a quality valve of the right type, and why you should never pull the check ball out.

Fuel Demand Valves: Troubleshooting the Valve That Holds Back a Sealed Tank

Modern EPA-compliant fuel tanks stay sealed and build pressure in the sun, and a fuel demand valve keeps that pressure from pushing gasoline into the engine when it's off. Learn how it differs from an old-style ball anti-siphon valve, the symptoms of one that sticks closed or leaks through, how to rule out cheaper causes first, and why the replacement must be the same type, never a ball valve.

Fuel Pump Checks - Is It the Pump or Something Starving It?

Bogging at speed, surging or dying after a few minutes is often blamed on the fuel pump, but vents, filters, primer bulbs and anti-siphon valves cause the same symptoms. Learn how mechanical, pulse and electric pumps work, the safe checks you can do, what the primer bulb is telling you, and why a real pressure test needs the right gauge and the factory spec.

Guardian, Limp Home and Reduced Power Modes: Why Your Engine Cut Power and What to Do

Modern outboards and inboards cut power on their own when a sensor reports trouble. Learn what usually triggers Mercury's Engine Guardian, Yamaha's RPM reduction and other brands' limp-home modes, how to read the warning, and how to decide between idling home and stopping to call for help.

How to Bleed Air From a Marine Diesel Fuel System

A diesel that sucks air after a filter change, a fuel leak or running the tank dry may not start until the air is pushed out. Learn the order that works on most older mechanical diesels, why common-rail engines are different, how to protect the starter and exhaust while cranking, and the high-pressure fuel dangers you must respect.

How to Check and Adjust Boat Shift and Throttle Cables

Hard shifting, a lever that will not go fully into gear, or a gear that lands in a different spot every time usually point to the control cables. Learn how to find out whether the problem is the cable, the control box or the engine, how to adjust the cable ends, and when it is time to replace both cables.

How to Check and Top Up Power Trim and Tilt Fluid

Check and top up the hydraulic fluid in your power trim and tilt unit, then work through the simple checks when the motor won't go up, won't go down or slowly sinks. Most trim problems are a dead battery, a bad relay, low fluid or a release valve left open, and you can find those yourself.

How to Check for Worn Outboard Motor Mounts

A clunk when you shift, buzzing vibration at idle or a motor that wobbles side to side can mean the rubber mounts between the outboard and its bracket are worn out. Learn how to rule out the cheap causes first, check the mounts yourself and know when replacement belongs in a shop.

How to Clean the Carburetor on a Small or Older Outboard

Old fuel turns to varnish and plugs the tiny jets in a carburetor, so the engine only runs on choke, surges or will not idle. Learn when the carburetor really is the problem, how to drain and clean it, and when a rebuild kit or a replacement makes more sense.

How to Do a Compression Test on an Outboard, Sterndrive, Inboard or PWC

A compression test tells you whether the pistons, rings, valves and head gasket in each cylinder are sealing. Learn when to do one, how to do it safely, how to read the numbers by comparing cylinders, and what a wet test and a leak-down test add.

How Water Gets Into Boat Fuel (and How to Stop It)

Water in the fuel is one of the top causes of rough running and dead engines, and it almost always has an entry point you can find. Work from the jar test through the fill cap O-ring, a recessed deck fill, the tank vent, the sending unit gasket and your washdown habits, and learn how much condensation really matters.