Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 58Get this manual
Troubleshooting with the Digital Diagnostic Terminal
Troubleshooting Without Digital Diagnostic Terminal
Troubleshooting without the DDT is limited to checking resistance on some of the sensorsTypical failures usually do not involve the ECMConnectors, set-up, and mechanical wear are most likely at fault Verify spark plug wires are securely installed (pushed in) into the coil towerThe engine may not run or may not run above idle with the wrong spark plugs installedSwap ignition coils to see if the problem follows the coil or stays with the particular cylinder
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NOTE: 1998 Model ECMs are capable of performing
a cylinder misfire test to isolate problem cylindersOnce suspect cylinder is located, an output load
Outboard ECMs