The water separator warning went off on an F175, you drained the filter bowl, the engine runs fine again, and the message still sits in memory. Clearing it now is the obvious next step and also the right one. With an app, clearing takes seconds. The real decision is about timing, because once the memory is empty it can't tell you anything later.
Times when clearing is the right call
- After a fix you can name. You replaced the TPS, cleaned a corroded shift switch connector or drained water from the fuel filter. Clear, run the boat, read again.
- After a known one-off. The lanyard pulled during launch, or the battery went flat over winter and the memory filled with low voltage and sensor messages from a slow crank.
- Before a test run when you want a clean baseline, provided you saved the old list first.
Times when it only hides things
- Before the cause is found. An intermittent message you clear and forget comes back, usually on the worst day of the season.
- After the engine went into reduced power. The stored message is the only record of why. Clearing it before a mechanic sees it costs them time and costs you money.
- Overheating or oil pressure messages. Clearing and running on to see what happens is how powerheads get ruined.
- Selling the boat. An empty list fixes nothing, and a list of old messages with notes on what was done about them builds more trust with a buyer than a suspiciously clean one.
A workflow that keeps the evidence
- Read the memory with the M-JET Diagnostic and screenshot the full list, plain-text descriptions included.
- Note the conditions: how long the engine had run, what it was doing when the alarm came on, flat water or chop.
- Work through the check steps the app shows for each message. Most of them start at the wiring and the connector, and it's tempting to skip that first step. Don't.
- Fix what you found. Then clear.
- Run the boat under the same conditions that triggered the message, and read again.
The screenshot is the step people skip. If the message returns three weeks later, you'll want to know whether it's the same one, and whether it came with company.
On a boat that more than one person runs, add a line to your notes about who cleared what and when. A memory cleared by a well-meaning friend after a weekend trip leaves the next person staring at an empty list and an engine that still drops into reduced power halfway through the throttle range.
What clearing doesn't do
Clearing erases the record. It doesn't replace a thermostat, empty a separator bowl or fix a pin. If the condition is still there, the ECU sees it again and logs it again. How fast depends on the fault. An engine shut-off switch that's still open shows up again right away. A knock sensor message or an overcooling message may need heat, load and a proper run before it reappears, which is exactly why a quick idle in the driveway proves nothing.
What you can clear also depends on the engine. The app offers clearing where the ECU supports it, so an older F90 and a newer F300 may behave differently. The page about clearing fault codes has the details. When a message keeps coming back after a repair, go back to its plain-text description and check steps and start again from step one, including the connector you were sure you already checked.
