Thank's, have tested the motor on land with analog and digital meters along DVA volts readings on the entire electrical components, all were found inside their factory parameters stated on the Service Manual. Don't imagine myself running a tiller motor at speed with removed cowl and hocked instruments troubleshooting electrical components one at a time. Electrical components have 3 working stages : Works spot on, are fully kaput or with erratic intermittent electrical misbehaviours, being the latter the most complex to correctly troubleshoot as Paul has experienced himself. Being a cautious boater count with all the electrical components to swap and test so easy peachy. Who said that boating was a cheap water sport LOL!!
Been doing all those basic electrical testing/troubleshooting methods when trying to find the culprit that doesn't let the motor to run properly specially at wot. This is the entire electrical system of such simple motor :
This is the exciter coil Ohm test :
This is the primary ignition coil Ohm test :
Both within their factory Ohm values. Tested the DVA outputs of the exciter coil and the CDI while cranking, both were found within their respective DVA values. Troubleshooting electrical components under both test won't guarantee to find the culprit fast enough if any one of them misbehaves intermittently and erratically, that's heats up, shorts, works ok when cooled to miss again eternally. On such case scenario new parts swapping one by one it's mandatory if wanting to be on the water asap. Could be a costly parts swap but who said that boating was a cheap sport....LOL!!
And the......bummer goes on. Installed a brand out of the box CDI unit, tested the combo lightly loaded and exact same. The motor hesitates 2 minutes after has been idling at neutral after a 20 minutes run at 3/4 throttle. It would be the last straw being the Exciter Coils the one that's failing ? An EC swap working with a new Ignition Coil and a new CDI is in order. fingers crossed!!
Nope, all electrical components grounds and the powerhead's threads where they bolt onto are in a shinny state...
Swapping and installing a very low hour use Exciter Coil from other motor yielded mostly the same, hesitates bit less than on previous tests.
Conclusion : none of the 3 new electric components were found with intermittent issues. I'm inclined to think that's a faulty cylinder head gasket, a new non OEM head gasket was installed at 500 run hours, seems is letting micro water droplets to enter the combustion chamber and motor to hesitate, misbehave when pushing 450 Kg of load at 1/4 throttle.
Once passing that setting can run super strong at wot all day long with 0 issues, spark plugs confirms a very neat combustion when running wot.
Lesson learned never buy non OEM parts, will fail prematurely...
