Mercury 2.5 Trigger/Flywheel Magnets

[kbahus]

New to the site and looking to get some advice about a newish to me 1998 Mariner 150 EFI, OG869606 on a Triton TR. Boat was purchased last summer and I developed a problem that seemed to be a misfire on Cylinders 1 and 4 at idle or when trying to get on plane under load. The symptoms were intermittent and it ran great on plane and sometimes achieved plane no problem. One consistent theme I noticed toward the end of the season was that once the motor was trimmed all the way down the misfire would develop, but would be ok trimmed level or higher. Wet plugs on cylinders 1 and 4 pointed me toward the trigger. I did a static trigger ohm test per the service manual and it checked out ok. I was able to notice that with my timing light running on the hose I would could watch the spark go haywire on those cylinders as I trimmed the motor down. Fast forward to today when I finally got the flywheel off and found a couple interesting things that hopefully have pointed me in the right direction. The trigger housing has hairline cracks in the plastic just above the pickup. Also, the flywheel inner magnet has tiny hairline cracks. I am absolutely replacing the trigger, but what about the flywheel? Should this be replaced as well, can the magnets fail? Does anyone believe that this could cause the misfire?

A couple other things I have noticed are some burned wires between the stator and voltage regulators, seems pretty common. I have not put the multimeter on the stator, switchbox, or voltage regulators yet but plan to. I wish Merc parts were not so darn spendy these days as I would replace everything. As it sits I am going to have track down clean used parts sadly. Also, this motor is completely stock with all black boxes etc in place.

[H2Okie]

You can get replacement parts from CDI and Sierra that are not only available but cheaper than Mercury parts .
A cracked magnet on the flywheel can act like two separate magnets and wreak havoc on timing . You can perform a simple test on the 6 magnets glued inside the flywheel with a compass . In one revolution moving the compass around the inside of the flywheel you should see 6 distinct "North" poles and 6 distinct "South" pole swings on the compass dial . A crack is bad and loose magnets that have lost their bond to the flywheel are bad to . iron shavings stuck to the middle of the magnet will also indicate a crack .

[tlwjkw]

A couple other things I have noticed are some burned wires between the stator and voltage regulators, seems pretty common.

heat build up with those bullet connectors cause lotsa problems... cut tha "connectors" off then solder and heat shrink... you'll be way ahead.

[ChrisCarsonMarine]

1 and 4 are fired by the same trigger coil...you probably have a bad trigger,Chris