Since you said cylinders 3, 6 and 5 threw the rods, it very well could have hydraulic'ed. 3, 6 and 5 are all together in the firing order, and if the motor was parked on the #6 exhaust centerline angle, the valves in 3 and 5 would be open too. My thinking is your engine took a gulp from the exhaust side through both tailpipes. Look closely at the height of your risers above the waterline.

No. Exhaust is like new. No issues there.

The issue started while the engine was still running. Water didn't go up the exhaust. It was running good at speed, then slowed to idle and it was running horrible like missing cylinders, then tried to give throttle again and stalled.

That's when the starter issue came about. And then again after 20 mins it started with no issue and ran perfect.

Starter actually quit after idling to in to the ramp. I tried to start it again on the trailer and it would no longer engage.

Well 1st very sorry that SUCKS!!! I feel she drank some water man......

I am not doubting that water was involved. I just don't in any way feel it came back up the exhaust like from a wave or something.

This website is like medical websites for rookies like me. It makes me paranoid that I am going to experience all of the same problems lol!. You knowledgeable guys don't know how lucky you are. What are the first signs of Reversion that I should watch for to prevent total failure?

Well, then I guess this thread is like a post mortem. Reversion can be tricky to track down. Depends on severity - if it's really bad oil will get milky and actual oil level might rise. However, you can also have "stealth reversion" where oil doesn't really get milky - you just have smaller amounts of water dripping into the exhaust ports and getting belched back out. This might manifest itself as an engine that wants to idle rough and stall out. Only way to find it in this case is to look for water on the plugs, or plugs that look "steam cleaned". Only surefire way to detect it is to pull a riser or header after idling and look for water in the ports. The trouble with this kind of reversion is that it might not rear its ugly head until after you have made a high speed run and got the exhaust valves nice and hot, and then pull the sticks back to idle and drop some cold water on those valves and blammo! Game over.

I think it's important not to assume the fuel issue and the thrown rods are related. Coexistence does not imply causation. Try to separate these two in your mind until you can deduce logically that the two were related.

What did the #4 rod journal look like? Was failure imminent there due to heat from #3 failing? I'm trying to understand why #6 failed. Did that cylinder hydrolock or was it collateral damage? Any evidence?

Any signs of water leakage into cylinders 3 and 5? Cracked head? Block cracked between the bores?

Did this engine overheat recently?

While it does suck, inevitably what has happened is that your bank account balance has gone down and your credit card balance has gone up. Just keep everything that could have gone wrong in your mind and try to correct it when you build the new motor.

Even if something you think was possible wasn;t the cause, the more weak points you eliminate, the more more bullet proof the new motor will be,

OP - for your own info (and if you didn't know) the ZZ502 cam is similar to the old hp500 cam. I think Merc had some problems with that cam water sucking so they switched exhaust/risers, if I remember correctly. Anyways.... I had a ZZ502 in my boat for about 5 years. Ran it one season with the stock Merc exhaust, that had the 3 inch risers. No known problems with reversion. However being aware of the 110LSA and water sucking potential, after idle time I'd crack the throttle a couple of times to clear the exhaust of water that may have accumulated. Like I said, no known problems but the 110LSA was always on my mind.