Trim problems mercruiser 3.0 troubleshoot

[MS Tarheel1]

Have a 2004 S/R Sport 180 with 3.0 Sterndrive. Parked with cover on it since October. Pulled cover off to check interior of boat and much to my dismay...there was 8-12 inches of water inside boat from very heavy rains and drain plug still in. I pulled drain plug and it literally took 45 minutes to drain. I rinsed inside of boat back to normal. Charged battery the next day after allowing some drying out. Battery back to 12.6V. Now when I depress the trim switch up or down....nothing happens. I hear silence. Nothing. Stern drive is in full down position.
Any suggestions on where to look? Is there a fuse holder or electrical connection I need to check for wetness/corrosion? As always....I appreciate your insight.

 

[DWABoat]

Wow. Where to start. I have dealt with this before. How long was the water sitting in the boat? Weeks, months?
I would disconnect the battery first.
Then determine the waterline to see what was submerged.
You have a starter, trim pump, possibly and electric fuel pump, miscellaneous wiring in the bilge area, electrical modules, etc.
Inspect the electrical connections for corrosion. The starter may need service, if it sat submerged for a long time. I changed mine because I did not want a failure on the water.
Your trim pump solenoids, if they sat submerged are likely toast. They are easy to change and cost about $20 each.
Make sure you don’t have water in your trim pump reservoir.

 

[Scott06]

Check
1. 50 a circuit breaker on engine. Mine is located just behind carb, I think on 3.0 it’s on the back left
2. connection at the starter likely it was under water this is where 12 v from battery feeds the starter, the trim pump and 12 v to boat. There is also a 90 a fuse next to starter lug. It may have blown. It’s a small cube.

if water was high enough it may have gotten into engine and bellows so check your engine oil and maybe pull the drive to check gimbal bearing and u joints if it was that high.