Lots of white smoke, starting problems

I have had the boat on the water in the marina over winter (mild winter in London). The boat got full of rain water and the engine was partly immersed for a few weeks at least. The engine is a mercruiser 4.3 on a Glastron 185 cir2007. I have been trying to start the boat over the last 6 weeks and performed the following:
Removed water from fuel filter
Changes spark plugs and cables
Changed coil

Managed to start briefly but white smoke was coming at pressure from vent on top of piston cover on both sides. Checked oil level which was higher than normal. Suspected that it is mixed with water. Extracted all oil and water, changed filter and new oil.

I used to get very little oil leak from behind the starter motor and I suspect that's where water has gained entry from.

The engine started for almost 2 min still smoking heavily from vent then stalled and smoke came from everywhere around the engine. Attempted to restart. Engine turning but could not start.

Please see 2 videos of smoke.
https://drive.google.com/file/d/0Bz4ozXTWG1EeeGJWQ0xHXzhlM0k/view?usp=drivesdk
https://drive.google.com/file/d/0Bz4ozXTWG1Eeb2VfeWlkQkdGS0U/view?usp=drivesdk

I have a feeling that this is bad news this time. Any help greatly appreciated.

It just might be the video, but that thing sounds awful! Will it restart?

Jeff

running it at elevated RPM with water mixed with the oil in the crankcase surely didn't help. Having the water sit inside the engine for 'weeks' is another downer.....

given your description of what happened and what was done, the 'white smoke' isn't surprising....

have you checked for water in the fuel tank??

I'd also clean out the distributor cap - its got to be full of moist stuff too.

finally, was there any water in the cylinders when the plugs were changed? and the last video, towards the end had either boiling water or dripping water - was the temp gauge showing normal or hot?