Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 62Get this manual
1998 DFI Troubleshooting without DDT 1998 OFI Troubleshooting Guide Symptom 1Engine cranks but won't start Cause 1.1 Weak battery or bad starter motor, battery voltage drops below volts while cranking (ECM cuts out below volts) (Fuel pump requires volts) 1.2 Low air pressure in rail (less than 70 psi at cranking) Action Replacecharge batteryInspect condition of starter motorCheck condition of battery terminals and cables
Inspect air system for leaksInspect air filter for plugging (air pressure measured on port rail)Inspect air compressor reed valves if necessaryCheck that primer bulb is firmKey-on engine to verify that fuel pump runs for seconds and then turn offMeasure fuel pressure (valve on starboard rail) Fuel pressure should be 10 psi greater than the air pressureCheck for fuel leaksIf fuel pressure leaks down faster than air pressure, seals on fuel pump may be leakingCheck air system pressure, see 1.2Remove flywheel and inspect keyReplace fuseInspect engine harness and electrical componentsCheck lanyard switch Listen for relay to "click" when the key switch is turned on