95 Mercury 115 ELPTO Repeatedly Blowing Rectifier / Switch Box

Joined
Aug 25, 2022
Messages
7
Hi, hoping for some guidance. I'll try to keep it clear. I purchased a used non running 95 Ranger with a Merc 115 ELPTO 2 stroke outboard. It would not run well. The tach moved wildly. I found a cooked yellow wire on the rectifier, replaced it and found it ran better but not right. Replaced the switch box and the engine ran very well. The tach worked proper. Both were Amazon Chinese replacements. After about 2 hours on the water run time both units failed. Once again the tach went haywire. Being there is no mechanic within 40 miles that will work on 2 stroke outboards, after researching, I replaced the stator, trigger, rectifier and switch box. The first 3 are CDI US made parts. The switch box is Chinese (I ended with 2 from the first order). The engine now runs well but after about 1.5 hours the tach went haywire for only about 5-6 seconds at a low cruising speed of around 1800 RPMS. If I was not looking at it I could have missed it. I ran the engine for another hour with no issues (all RPM's, mixed starts and stops). I suspect there is still an unprepared issue lurking.
Battery is a correct marine flooded traditional unit, fully charged.
Connection is wing nut with starter leads on the bottom of the stack. Cables are clean. Will change to proper clamps.
Ran the CDI suggested test for the ignition key and found no shorts.
Inspected as much of the wiring in the engine as possible and found nothing afoul.
What would cause the tach to have intermittent wildness?
Dave
 

Dave1027

Lieutenant Junior Grade
Joined
May 25, 2010
Messages
1,080
The tach is connected to the charging side of the Stator. The switchbox is also connected to the stator but on the ignition side. Does your motor have the higher output stator with voltage regulator?
 
Joined
Aug 25, 2022
Messages
7
No, it has the external voltage regulator. I think the stator is the 16 amp. And those parts are new CDI. I beleive there were capactiive discharge systems around this time but my engine is NOT the capacitive discharge system.
 
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