Repair & maintenance guides

How to Test a Marine Diesel Lift Pump (Feed Pump): Flow Test, Vacuum Gauge and Warning Signs

The lift pump pulls diesel from the tank through the primary filter and feeds the injection pump. When it weakens, the engine starts hard, loses power or dies. Learn how to find it, tell a mechanical pump from an electric one, check it with the priming lever, run a simple flow test into a clear container, read a vacuum gauge on the primary filter, and spot a leaking diaphragm before it fills your oil with fuel.

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.

Jet Outboard Impeller Shimming and Sharpening: Win Back Lost Thrust

Gravel and sand slowly round off a jet impeller's edges and open the gap to its liner, and the boat loses push. Learn the signs, how to make the motor completely safe to work on, how moving thin shims closes the gap, and how a light touch-up on dull blade edges can restore performance.

Jet Ski Intake Clogged with Weeds, Rope or Rocks: How to Clear It Safely

Engine revs high but the jet ski barely moves, or an overheat warning comes on? Something is probably stuck in the intake. Learn the symptoms, how to use iDF and similar features, how to clear the grate safely in the water, on the beach or on the trailer, and how to keep it from happening again.

Jet Ski Won't Start or Won't Beep: A Step-by-Step Check

Most personal watercraft that refuse to start have a simple cause: the key or lanyard, a weak battery, a blown fuse, a security lock or a flooded engine. Work through these checks from the cheapest to the most involved and learn what each result means for Sea-Doo, Yamaha and Kawasaki models.

Losing Coolant With No Visible Leak? How to Pressure Test a Closed Cooling System and Its Cap

When the coolant level keeps dropping and you can't find a drip, a simple hand-pump pressure tester can show where it's going. Learn how to test the system and the pressure cap safely on a cold engine, isolate the heat exchanger and coolant-heated appliances, and recognize the signs of a head gasket or internal leak that need a mechanic.

Loss of Power, Hesitation or Misfire - Troubleshooting Guide

Figure out why your engine bogs down, stumbles, will not reach full rpm or runs rough. Work from simple checks like trim, prop and fuel filter to ignition and engine protection modes before paying for diagnostics.

Low Oil Pressure Warning: What to Do on a Sterndrive, Inboard or Diesel

A low oil pressure alarm or a gauge that drops toward zero means the engine may be running without proper lubrication. Learn what to do in the first minute, the simple checks you can make yourself, how to tell a bad sender from a real pressure problem, and why you should never keep running on the alarm.

Marine Diesel Won't Start: Troubleshooting From Battery to Fuel

Work through the usual reasons a Yanmar, Volvo Penta, Westerbeke, Beta or similar marine diesel won't crank, or cranks but won't fire, starting with the free and simple checks. Most no-starts come down to the battery, preheat, air in the fuel or a fuel shutoff solenoid.

Marine Generator Won't Start or Keeps Shutting Down

A step-by-step troubleshooting guide for a boat generator (genset) that won't crank, cranks but won't start, starts and then dies, or runs without making power. Work from switches, battery and fuel to the safety shutdowns for low oil, high temperature and lost raw-water flow, without flooding the engine or risking carbon monoxide.

Marine Stereo Troubleshooting: No Power, Lost Settings, No Sound or Bluetooth Trouble

Track down a boat stereo that won't turn on, forgets its presets, resets when the engine cranks, plays no sound or won't keep a Bluetooth connection. Work from the free checks (switches, resets, fuses) to voltage tests, speaker wiring, water damage and software updates before you buy a new unit.

Milky Engine Oil or Water in the Oil - What It Means and What to Do

Milky, creamy or rising engine oil usually means water is getting into the engine. Learn why you should stop running it right away, how to tell harmless condensation from a real leak, and which parts are the usual suspects: head gaskets, exhaust risers and manifolds, intake manifold gaskets, oil coolers and freeze cracks.

No Spark - Safe Ignition Checks for Outboards, Sterndrives, Inboards and PWCs

Engine cranks but never fires, and you suspect the ignition? Work from the cheap, common causes (kill switch lanyard, key switch, plug wires and caps, plugs, battery) to a proper spark test, and learn what the stator, CDI and coils do and when it is time for a dealer.

Outboard Fell Overboard or Engine Got Submerged: What to Do in the First Hours

A dunked engine can often be saved, but only if you act fast and in the right order. Learn what to do (and what never to do) in the first hours after an outboard goes overboard or a boat swamps, how to buy time until a shop can take it, and when it is a loss.

Outboard or Sterndrive Rough or Surging Idle: Find the Cause, Cheapest Check First

An engine that shakes, hunts or surges at idle but runs fine on plane is telling you something specific. Learn how to read the pattern, then work in order from free checks (warm-up, tank vent, primer bulb, fuel) through plugs, air leaks, carburetor idle circuits and the idle air control valve, and know when it's time for a compression test or a dealer scan.

Outboard or Sterndrive Vibration - Troubleshooting Guide

Track down a new shake or buzz by noting when it happens (neutral or in gear, which rpm), then check the prop, hub, shaft, mounting bolts, motor mounts, engine height and misfires in order, from the simplest to the most serious.

Overheat Alarm: What to Do in the First 60 Seconds

A short, practiced routine for the moment the temperature alarm goes off: take the load off, look for cooling water, shut down if it isn't there, and check every space the exhaust runs through for heat or fire. Based on a June 2026 Coast Guard safety alert about a fatal fire that started with an overheat alarm.

Prop Ventilation vs. Cavitation - Why Your Engine Revs Up and the Boat Loses Grip

Sudden RPM spikes, blowouts in turns, or a prop that slips when you accelerate are usually ventilation, not cavitation. Learn to tell them apart, then work through the fixes in order: trim, load, prop damage, the hull ahead of the prop, engine height, and finally a different prop.

Remote Control Box Troubleshooting: Stiff Lever, Won't Crank, Trim Switch

The throttle and shift control at the helm (side-mount or binnacle) takes a beating. Learn how to find out why the lever is stiff, why the engine will not crank even with a good battery, why the trim button on the handle quit, and when the whole control box should be replaced along with its cables.

Spun Prop Hub - How to Tell, Quick Marker Test and Repair Options

If the engine revs up but the boat barely accelerates, the rubber or plastic hub inside your propeller may be slipping. Learn how a spun hub feels, how to confirm it with a simple marker test, the difference between pressed rubber hubs and replaceable hub kits, and your repair options.

Sterndrive Hard or Clunky Shifting: Cables, Shift Interrupt Switch and Cone Clutches

A sterndrive that bangs into gear, is hard to pull out of gear, stalls when you shift or hesitates and then slams in is telling you something about its shift system. Learn the checks you can do (idle speed, technique, cables, linkage and drive oil), what the MerCruiser shift interrupt switch and Volvo Penta cone clutches do, and when it's a shop job.

Sterndrive Power Steering: Fluid Checks, Hard Steering and Leaks

Troubleshoot the engine-driven power steering on a MerCruiser, Volvo Penta or similar sterndrive or inboard, from the free checks (fluid, belt, cable) to the signs that the pump or actuator needs a pro. Steering that suddenly goes heavy at speed is a safety problem, not a comfort problem.

Strange Engine Noises - What a Knock, Tick, Rattle, Whine, Grind or Squeal Can Mean

Learn what common boat engine noises often point to, which ones mean shut down now, and the safe checks you can do yourself before describing the problem to a mechanic.

Tilting an Outboard or Sterndrive by Hand: Using the Trim Manual Release Valve

When the power trim quits, a small release valve on the trim unit lets you raise or lower the motor by hand, so you can get off a sandbar, load the trailer or get home. Learn where to find it, how far to open it, how to lift and support the motor safely, and why it must be closed again before you run.