This is exactly what happened to me. 2007 launch 20 SSV with 325 Indmar. The shop spent 2 months troubleshooting and I had a bad ecm and a bad wiring harness. The order for the wiring harness was put in last week, so I’m still waiting on that. All in all, I’m about $2k in, missed most of the season, and still don’t have my boat back. Hopefully you have better luck.