83 Merc 115 switchbox failure cause

[gwukena]

83 Merc 115 s/n 7200692 propped for 5500 rpm

Had boat out last week, ran like top for two hours, weathered a storm out on the river, when went to throttle up, engine wouldn't break 1200 to 1500 rpm. Got home, checked spark, 2,4,6 dead. DVA testing done. Found lower switchbox toasted. Both switchboxes were replaced two years ago with new merc units to correct loss of spark on #6. Engine has maybe run twenty hours max since.

Installed old good switchbox, fires on all six now. During compression test last night, lower switchbox stator terminals were too hot to touch, when red/wh lead removed from box, arced , could hear clicking from switch box.

Last year installed kohler voltage rectifier/regulator. Checked regulator, found yellow charge coil leads have voltage at all times. Did some research on regulator, half wave rectifier design, seems to be made to have voltage on coil leads at all times. I was wondering if this regulator could be causing stator issues and subsequent switchbox failure.

At the very least I know i'm probably going to have to buy two new switchboxes, ditch the kohler regulator and revert back to unregulated system or install a proper full bridge rectifier/regulator.

I've attached a pdf of testing done.

Thanks for your help
Gary

View attachment Microsoft Word - Outboard troubleshooting #1.pdf

 

[gwukena]

Re: 83 Merc 115 switchbox failure cause

Any ideas

 

[Sunfish12]

Re: 83 Merc 115 switchbox failure cause

Disconnect the rectifier, tape off yellow wires and see if stator wires still get hot and DVA test it. I would pull the flywheel and check for any heat damage.

 

[gwukena]

Re: 83 Merc 115 switchbox failure cause

Already have flywheel off, no obvious signs of heat damage. No problem with wiring at stator junction, no rub marks on flywheel, upper bearing good, seal good. There does appear to be some distortion in the encapsulation at the front part of stator, appears to be where there are two coils hidden. Can post pics tomorrow once it's light out again.

I suspect the kohler regulator may be causing my problems. Will reinstall flywheel and retest with regulator disconnected.

Thanks

 

[gwukena]

Re: 83 Merc 115 switchbox failure cause

Fixed. Thanks for all the replies

 

[j_martin]

Re: 83 Merc 115 switchbox failure cause

Fixed. Thanks for all the replies

Could you tell us what fixed it?

 

[gwukena]

Re: 83 Merc 115 switchbox failure cause

Spoke to old buddy from back home(dealer). Stator, switchboxes, back to unregulated charging circuit.