Jet Ski Taking On Water: Find the Leak and Drain It Safely

After a normal ride, pull the craft out, keep it level and remove the seat. Note roughly how much water is inside and where it pools (front, around the engine, at the stern by the pump). Ask:

• Does it happen at idle or sitting at the dock? That points to something below the waterline: plugs, the driveshaft seal, a hull crack.
• Only when riding fast or in chop? That points to seals, hoses or vents that only get water under pressure or spray.
• Only after reboarding from deep water or with a heavy load? Often normal spray past the seat seals.

On the trailer, with the bow higher than the stern, remove the stern drain plugs and let the water run out. Yamaha's post-ride routine is to open the stern drain valves, rinse the bilge, then raise the bow so all the water drains and the hull dries. Mop up what is left with a sponge or wet-vac, and leave the seat off so it can dry.

Plug practice differs by maker: Yamaha's global post-operation advice is to keep the drain plug out while the craft is on land, while Yamaha's US storage checklist says to make sure the plugs are installed. Follow your manual, but always put a reminder on the steering or tow vehicle whenever the plugs are out.

A plug that is loose, cross-threaded or missing its O-ring lets water in steadily, even at the dock.

• Inspect each plug and its O-ring or gasket for cracks, flattening or sand.
• Clean the threads in the plug housing.
• Yamaha's pre-ride check says to make sure the plugs are correctly installed, and to lubricate dry fittings with marine grease.
• Tighten firmly by hand or as your manual describes. Do not crank on them with tools so hard the housing cracks.

Sea-Doo's launch advice is simple: install the drain plugs before you back down the ramp, and loosen them after you pull out.

Yamaha notes that worn seat and hatch seals let water in and recommends treating them with a silicone protectant. Look for rubber that is torn, flattened, cracked or pulled away from the edge, and latches that do not pull the seat down tight. Water that enters this way shows up mostly after spray, waves over the deck or deep-water reboarding.

With the seat off and a flashlight, follow each hose you can see: cooling water lines, exhaust hoses, bilge hoses and the water box or muffler connections. Yamaha's post-operation checklist includes checking exhaust and cooling hose clamps for looseness and corrosion.

• Snug loose clamps. Replace rusted ones with stainless clamps of the same size.
• Replace any hose that is cracked, split or soft.
• Look for white salt trails or rust stains that show where water has been escaping.

A loose or split exhaust connection is especially important: it can let hot exhaust and water into the hull and, on some models, into the engine. If you find one, do not run the engine until it is fixed.

• Suction (siphon) bilge: small hoses run from the low point of the hull to the jet pump area. If a hose is cracked, kinked, disconnected or its pickup is clogged with debris, water stays in the hull while you ride. Clean the pickup screens and blow through the lines if your manual allows.
• Electric bilge pump (if fitted): test it, check its fuse, and make sure the outlet is not clogged. See our bilge pump guide for the general method.
• A failed one-way valve or a hose connected backwards can actually siphon water in when the craft sits. Compare against the diagram in your manual.

The driveshaft passes through the hull from the engine to the jet pump, and a seal keeps water out at that point. It is a wear item on every personal watercraft and one of the most common causes of serious water in the hull.

• Sea-Doo uses a carbon ring seal pressed against a ring on the shaft by a rubber boot.
• Yamaha and Kawasaki typically use rubber seals in a bearing housing, often with a grease fitting.

With the seat off, look at where the shaft goes through the back of the hull. Signs of trouble: water collecting right at the seal, a torn or cracked rubber boot, loose boot clamps, black carbon dust (on carbon ring seals) or a dry grease fitting. Many manuals list a seal or bearing housing check and a greasing interval: follow yours. Running the engine out of the water longer than the manual allows, worn engine mounts or misalignment can wear the seal faster.

Replacing the driveshaft seal usually means removing the jet pump and shaft and checking engine alignment. Most owners leave that to the dealer.

Look under the stern at the jet pump mounting, ride plate and intake grate. Missing or loose bolts, a damaged pump seal or a cracked area where the pump bolts to the hull can let water in. While you are there, check the intake grate for damage; our jet pump guide covers the pump itself.

Hulls crack from beaching, hitting submerged objects, poorly adjusted trailer bunks or jumping waves. Yamaha's pre-launch checklist includes checking the hull for damage, soft spots, blistering or cracks. Check:

• The bottom, keel and the area near the intake, especially after beaching on rocks or shells
• The bond line where the deck and hull are joined
• Holes for accessories such as speakers, cleats, mirrors or reboarding steps, and screws added by previous owners
• Inside the hull with a flashlight, for cracks or wet patches that keep coming back

Pick the gentlest test first:

• Fill test (on the trailer): with the plugs in and the craft level, pour a few gallons of water into the hull, then look underneath and around the stern for drips. Drain completely afterwards.
• Dock test: with the seat off, a helper holding the craft at a dock in calm water and the engine off, watch inside with a flashlight for 10 to 15 minutes. Look first at the plugs, the driveshaft seal and the pump area. Do not run the engine while you are leaning into the compartment.
• Pressure test: dealers can pressurize the hull with low air pressure and spray soapy water to show tiny leaks. Too much pressure can damage seals, so leave this to a shop.

Leak only shows up after half an hour of riding? That's a common forum puzzle, and it usually means water gets in only under load or when hoses get hot: cooling hoses and their fittings, exhaust and water-box hoses, freeze plugs on the engine, or bailer (bilge) lines that have been reconnected backwards and now push water in. Experienced riders find these by watching inside while the craft sits in the water on its submerged trailer, securely strapped down, with a helper giving it a little throttle so the engine and driveshaft are under load. Keep hands, hair and loose clothing well clear of the moving shaft, and let a dealer do this test if you're not comfortable with it.

If the water level got high, check:

• The air filter and air box: Yamaha recommends checking the air filter for signs of water intrusion. A wet filter or water in the air box is serious: do not start the engine; see the dealer.
• The engine oil: milky or rising oil means water may be in the engine.
• The electrical box and connectors: corrosion or water inside means you may see electrical faults later. See our PWC electrical troubleshooting guide.

On the water, a flipped craft should be rolled back upright in the direction shown on the decal at the stern (often printed upside down so you can read it when the craft is overturned). The boater-education course material used by many states warns that rolling it the wrong way can damage the craft; the usual concern is water running into the engine through the air intake or exhaust. If there is no decal, learn the direction from your owner's manual before your first ride.

Back on land, do not try to start it. Get it on the trailer, drain the hull, and follow the capsized or submerged watercraft procedure in your manual if it has one. Otherwise take it to a dealer the same day if possible: water in the cylinders can bend internal parts when the engine cranks, and salt water corrodes quickly.