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.

Are the ends of any valves broken off?

No, no visible damage to the heads at all. They are being gone through now so I will find out for sure if they suffered any damage when the shop calls.

Piston tops should say it all...... See if they are steam cleaned man....

The pistons that the rods broke actually do look a little cleaner than the rest. And I would assume the cylinders that I would call the center of the engine would get water first if it was sucking back through the exhaust as they are directly in line with the riser.

I could be wrong, still trying to figure this out to make sure it never happens again!

Yep, #6 definitely looks steam cleaned to me, and 3 and 5 are suspect too.

Any reason you are running a 6-quart pan on there instead of an 8 or 10? That is one thing I would change for the next motor, assuming you have room.

Yes, the reason is that the person I got the boat from said they marineized 2 zz502's but really what they did was put 2 100% car engines in a boat. Proper oil pans are in the works!

The absence of carbon deposits on the perimeter of the piston tops says detonation. When you take the pistons out I think you'll find the top ring land tried to lift.

And what causes detonation?

Anyone think it started misfiring and the dead hole caused it to suck water back in? Usually happens with a valve issue but maybe the bad skip was causing it to pull water? I also agree that lowering the idle to 750 is better for bravos worse for reversion

Usually too much advance timing and or lean fuel mixture but low octane rating is another thing that can cause it. Detonation is actually pre-ignition, the fuel/air mixture ignites too soon prior to the piston being at TDC and the flame path isn't uniform. Carbon deposits can also get hot and cause detonation. What it does to the piston is in effect like you took a sledge hammer and hit the top of the piston, that in turn hammers on the rod bearings and drives the oil film out of the bearings. The end result is what happened to your bottom end.

Lack of fuel, too much timing, bad fuel, excessive heat, or not enough octane for compression ratio

Keep in mind that reversion can produce detonation too. The water cannot compress, which can raise the CR through the roof. Notice that the carbon is blasted away from the quench area. You see a perfect outline of the chamber on the top of the pistons. The water cannot compress in this area, and essentially blasts all the carbon off.

I'd think if reversion was the culprit there'd be at least a minimal amount of rust on the cylinder walls. My thinking is the carbon was burned off. I don't see any evidence of water being present in the combustion chambers.

I'm with payup on this. Those pistons don't look steam-cleaned to me. That looks like the carbon was detonated off. Steam cleaned pistons are clean as a whistle.

Detonation can also occur at startup, which might explain your starter problems. Detonation can cause the engine to kick back, taking out the starter. Take a look at your distributor (if applicable) and ensure the advance weights aren't frozen. Also check your cam timing and make sure the timing set didn't skip a tooth (although they usually skip in the retard direction, which wouldn't cause this issue).

As a confirmation, look at the insulators on the spark plugs. The carbon that was blasted off the piston crowns tends to deposit on the ceramic, and looks like pepper.

those pistons aren't steamed cleaned.those pistons hit the head after the bearings went totally away.now why did they do it.look at the bottoms of the piston and upper bearings.take pics and post.but you did have the head gasket gone for a little bit.notice the loss of the fire ring.

There are no upper bearings left to take pics of. Head gaskets look like new.

between the cylinders is burned,,gaskets weren't sealing.well look at the bottom of the pistons,,do they have burn oil on the bottom?

I don't think the pistons hit the head, especially with the rods bent. The reason the carbon is gone from the perimeter of the piston is because that's where the least material is because of the proximity of the ring land and that's what gets the hottest. Usually you'll see the ring land try and lift because the ring is trying to stick to the cylinder wall and the ring land is weak from the heat and can't hold the ring in place.

Well based on the color of the crank it did not have any oil going to the rods journals. Did you have an oil cooler installed or a remoteoil filter put on incorrectly?

lets see a pic of the heads.
the nice straight line of the cleaned portion on the piston,,thats the combustion chamber.rods bent after the crank smashed them out the block.bearings when the go that bad,let the piston smash the cylinder head.seen it many times.just need to see why the journls lost oil pressure.

Read post #61. Do you see any marks on the piston where it smashed into the head? No indentations or marks at all. Detonation causes the oil film to be hammered out of the rod bearing surface. That's why you lose the bottom end. Oil pressure wasn't lost until the bearings failed.

yes I do,pistons 3,5 and 6.

I also think you had oiling issues, the crank is blue from lack of lube, now either it spun a bearing and you kept running( not that hard to do as sometimes don't notice much) ran low on oil starved it, or their was fuel in the oil and diluted it, does not take much and will KILL it in a very short time...carb ever flood ??

Looking at the fact that it has the small automotive type oil pan installed and was likely not properly marinized, I have to also wonder if the 11 lb oil bypass valve was being run in it, which very likely resulted in hot dirty oil being routed to the bearings.

I had a friend that had a catastrophic engine failure due to 11 lb spring in a ZZ502. It took out bearing in the first few hours of hard running. But this engine had almost 200hrs on it. I agree the oil pan might not be optimal, but for 199hrs it was acceptable.

Rookie, I'm with you on the oil pan probably not being the issue here. I ran the same pan on a warmed over 454 for years without issues. However, it may have been possible that the bearings were able to hang in there for the 200 hours if he was changing his oil regularly and keeping it just fresh enough to make it to the next change. Then he comes to this season with some marginal bearings and a tank of bad gas that starts some detonation - might have been just enough to push it over the edge.

We can play post mortem all day, and we still might not ever find the smoking gun in this catastrophe. All he can do is try to build it better next time and correct the issues that were wrong with this one.

So where are all the extremely opinionated oil brand loyalists ? You would think with the answers on 'What type of oil ' threads, that there would be some of those voicing opnions here.

Goes to show you that.........LOL...

When a motor detonates it cooks the oil. If he had a stock cooler and oil that doesn't take heat very well it all would play a part in it.