2002 merc 75, 4 stoke no spark issue

I am a newbie to boating.

I took my boat out for a test run on the water last week, the stator may got some water from the ocean as I mounted the fish finder way too low and it created a big roster tail. Anyways, after the water got into the flywheel, my engines stopped in the following 2 mins... I could not start it anymore....

I took her home and found out the four plugs has not sparks whatsoever, I replaced the starter, solenoid and still no sparks. I suspect its the stator is cooked.

I also checekd, my newly changed engine oil level, it is way over the max and it is looks like milky. I knew there is water in it.

I wonder if I need to dump all the engine oil now/replace it with the filter now?

I also pulled the plugs and it appears their might water/oil mix in the engine head as well. I am not sure what the next steps to drain all of the exisiting bad oil from the engine head?

any insight is appreciated.TIA

report back, here's waht worked for me,

i) how to get sparks back?
1) replaced all spark plugs 2) replaced with a new starter, wires/solenoids 3) full charged batteries!! last time i checekd I did not sufficient juice to crank it.
ii) removed 1.2L engine oil
iii) checked fuel lines, clamps are air tight. Using some ( little) starting fluids voila, it worked. Tested current for both batteries at 13.46 charging.
iiii) I also dumped the old fuel in the floater, and bleeded all old fules from the old fuel tank about 50L.. To my surprise, the first 1L down the bottom is water and I can see it thru after I extracted the mix out.
Good luck and PM any info i you need , I will try my best to answer and share my experience.