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

Remove the seat or open the engine cover and let it air out for a few minutes. Look for fuel or oil in the hull, loose or chewed wires (mice love stored jet skis), a disconnected battery cable, and water in the bilge. If the craft has water inside or recently flipped, read Step 10 before trying to start it.

• Make sure the lanyard clip or D.E.S.S. key is fully seated on its post or switch. On Sea-Doo, the key usually needs to click firmly onto the post.
• Clean the key and the post. Sand, salt and dried grime between them are a very common reason for no beep or the wrong beep. Rinse with fresh water, dry, and try again.
• Try your spare key. If the spare works, the first key or its lanyard is the problem.
• On a Yamaha with a security system, check the display for a lock symbol. Switching to unlock mode from the display (with your PIN) is covered in your manual.
• A brand-new or second-hand key that was never programmed to your craft will not start it. That needs the dealer.

Turn the system on as your manual describes and note the number and length of beeps and any message on the gauge. On many craft, one pattern means "key accepted" and another means "key not recognized" or "fault," but the exact meaning varies by brand and year. Look your pattern up in the manual rather than guessing from a forum.

No beep and a blank display at all usually points to power: battery, main fuse or a connection (Steps 4 to 6).

Personal watercraft batteries are small and go flat quickly from sitting, especially after winter storage. With a multimeter on the battery terminals, a reading well below a full charge means it needs charging (our marine battery guide explains the numbers).

Remove the battery to charge it. Sea-Doo's guidance is to disconnect the negative cable first, then the positive, and to charge the battery out of the craft on a dry, level surface. If it will not take or hold a full charge, replace it. A battery can show good voltage and still fail under the load of the starter, so have it load tested if you are unsure.

Corroded or loose battery terminals look like a dead battery. Clean both terminals and cable ends with a wire brush until shiny, reinstall positive first and negative last, and tighten firmly. Yamaha's WaveRunner maintenance guide warns that a terminal can be corroded between the surfaces and still look clean, so take each connection apart and clean both faces; it also calls for hex nuts and lock washers, not old-style wing nuts, which work loose. Follow the negative cable to where it bolts to the engine and check that end too. Inspect the plug connectors at the key post and the start/stop button for green corrosion or water, and treat them with contact cleaner. Yamaha's season-prep advice is to clean corrosion with a wire brush and a baking soda and water paste, then coat the finished connections lightly with dielectric grease. A craft that starts fine but dies or loses its display when it hits waves usually has a loose battery cable or ground, so check these first.

Find the fuse box using your manual (often near the battery or under the seat or a cover). Pull each fuse and look at the metal strip inside. Replace a blown fuse only with the same type and amp rating. If a new fuse blows again right away, there is a short circuit: stop and take it to the dealer. Never fit a bigger fuse or bridge it with wire.

• A weak battery is still the most likely cause: a click with no crank often means not enough current.
• Check the jet pump. With the lanyard removed and the battery disconnected, look into the intake grate from under the craft. Rope, weeds, sticks or a rock jammed in the impeller can stop the engine from turning. Clear it by hand only with everything switched off; our jet pump guide shows how.
• Some models only crank with the throttle fully released or the controls in a certain position. Check your manual's starting procedure.
• If the battery is strong and the pump is clear, the starter relay, starter or start button may have failed. That is a dealer or experienced DIY job. A relay or its plug that looks green or crusty, or feels hot after a start attempt, is a common culprit owners report; stop trying to start it and have it replaced, because a connection that heats up can melt.
• Did it crank slowly for weeks before it quit? Slow cranking is an early warning of a tired battery, a bad cable or ground, or a dragging starter. Fix the cause instead of waiting for the day it won't crank at all.

• Fuel: is there fuel in the tank, and is it fresh? Fuel that sat all winter without stabilizer may be stale. See our ethanol fuel guide.
• Flooded engine: cranking over and over, especially after a few short tries, can flood it. Many fuel-injected watercraft have a flood-clearing procedure in the manual (on some, holding the throttle while cranking cuts off fuel). Use only the procedure for your model, and crank in short bursts with rests between them so the starter does not overheat.
• Spark plugs: older two-stroke models foul plugs easily. If you are comfortable doing so, check them as in our spark plug guide.
• Testing on the trailer: once it cranks, do not let it run out of the water for more than the few seconds your manual allows. For a longer test, use the factory flush attachment and the order your manual gives; Yamaha's is to start the engine before turning the water on, and to turn the water off before stopping the engine.

A check-engine light with reduced power usually means the computer has detected a fault (overheating, low oil pressure or a sensor problem) and is protecting the engine. Two harmless causes to rule out first:

• A Learning Key or speed-limited key on a Sea-Doo, which is designed to cap top speed.
• A speed or acceleration limit set in the display, such as Yamaha's Drive Control settings on models that have it.

If neither applies, ride slowly back to the dock and have the dealer read the fault codes. Continuing at full throttle can turn a sensor warning into engine damage.

Do not try to start it. Water may be in the engine. Get it out of the water, drain the hull, and follow the capsized or submerged watercraft procedure in your manual if it has one; otherwise take it to a dealer as soon as possible. Cranking an engine with water in the cylinders can bend internal parts.

If you need a tow on the water, tow slowly. Manuals give a maximum towing speed because water can be forced into the engine through the exhaust at higher speed.

If the battery is good, the fuses are good, the key is clean and the craft still will not respond, or it shows a fault code you cannot clear, the next steps need the brand's diagnostic software. Bring your notes from each step, both keys, and the beep pattern or message you saw.