Mercury 225/9.9 kicker short issue

[Alaskahatch]

I have a 2006 225 Optimax with a 9.9 Kicker, both Mercury. The other day I was running the boat on the main engine, turned it off to fish and could not restart. Starter just did the tick tick tick. Got home on the kicker. Thinking it was a starter, bought a new one. Nope! Next checked the new batteries I just put in. Both almost dead. Went to recharge batteries and found one barely half full with electrolyte fluid. Took both batteries back under warranty and replaced with new in the boat. Went to start and tick tick tick....nothing. Long day of troubleshooting and found out that the kicker motor is grounding out somewhere on the engine itself which is causing the main engine not to fire. When I disconnected the kicker from the electrical panel, the main fires as normal. This just started. Any ideas where to start looking on a 9.9 mercury for a short to ground? Anybody else have issues with something like this?

 

[GA_Boater]

Disconnect the wiring to the rectifier in the kicker. A shorted rectifier can short to ground.

Also check for bare cables from the kicker to the panel and the under cowl wiring as well.

 

[Alaskahatch]

All wiring from the main engine to battery selector, battery selector to batteries was solid. Kicker motor only has to connections, one to the #2 battery on my selector and the ground on my distribution panel. When the ground for the kicker is connected, the main starting voltage is cut from 12.7 to less than 6 VDC. When I disconnect the kicker ground, I get full voltage to my main motor. So I have it narrowed down to the kicker. I will start at the rectifier. Is there a bench test for it? With the ground disconnected, I can't use my electric start on the kicker but I have the pull handle backup to start it. So odd this just started.