Boat in the water, trailer still on the ramp, a truck waiting behind you, and the F150 does nothing when you turn the key. Or it cranks happily and won't catch. Most ramp no-starts come down to a few simple conditions that the ECU can tell you about in seconds, and they're worth ruling out before anyone starts talking about the starter or the fuel pump.
Nothing happens when you turn the key
Engine shut-off switch
The lanyard clip has to be in place, and the switch behind it has to be clean. The live value for the engine shut-off switch shows whether the ECU sees it as on. If the clip is in and the value still says on, look for corrosion in the switch or in the wiring behind the helm. The ECU logs a message for this too, and its check steps start with the cord connection, then continuity at the switch.
Shift position
A Yamaha outboard won't crank in gear. On mechanical remotes a shift position switch tells the ECU whether the gearcase is in neutral. A switch that still shows continuity in F or R, or a shift cable that's slightly out of adjustment, keeps the starter from turning. On digital remotes the shift position sensors and a neutral judgement value do that job. Check the live value with the lever in neutral before anything else.
Power supply
Battery voltage at rest, then during a crank attempt. The ECU can log messages for the main power supply and the starter magnet power supply, and in both cases the check steps go to the fuse first, then the wiring. Newer engines with digital controls show a possibility to start value, plus the main switch signal and the start/stop button state, which narrows down a dead start button quickly.
It cranks but won't fire
- Immobilizer communication error. On engines with an immobilizer, a key or wiring problem shows up as this message. The app shows it in the fault memory, but it can't program keys or touch the immobilizer settings. The check steps go to the wiring and the input and output voltage.
- Pulser coil irregular signal. Without a clean crank signal, the ECU doesn't know when to fire the plugs or open the injectors. Wiring, coil resistance and output peak voltage, in that order.
- Fuel. Trigger the electric fuel pump as an actuator test and listen for it. A water in fuel filter message, or water you can see in the separator bowl, will also stop an engine cold.
- Low voltage during cranking. An engine can spin and still not start if the voltage sags too far for the ECU, coils and injectors to do their work.
The order at the ramp
- Lanyard clipped in, lever in neutral, battery switch on.
- Plug in the M-JET Diagnostic and read the fault memory.
- Check the shut-off switch and shift position values.
- Battery voltage at rest and while cranking.
- Fuel pump test, then a look into the separator bowl.
That takes a few minutes and covers most of what actually goes wrong. The won't start page goes through the remaining causes in more depth.
When it's mechanical
A seized starter, a flooded engine, water in a cylinder or a fuel tank vent that's closed won't show up in any live value. If the ECU reports everything in order and the engine still won't run, stop cranking. Water in a cylinder plus a few more hits on the key is how a no-start turns into a bent connecting rod, so pull the plugs and turn the engine over by hand before you try again.
