Water in Oil, What's Wrong?!?!?!?!

I recently bought a boat from a buddy, its a 1989 Sea Ray 200 Bow Rider and has a 4.3l Mercruiser. I went to start the de-winterization process and apparently he did not winterize it properly. I checked all of the plugs and found that there was a brass freeze plug in the transom so I put that back. I checked the oil and it was good so I got to the point where I was going to crank it so I could change the oil and run the stabilizer through and add some new gas. I hooked the muffs up to it and turn it over a couple times to get the gas flowing. It sounded great but a minute or two after I cranked it i noticed the exhaust manifolds were leaking. Right side worse than the left, so I shut off the engine immediately. I inspected them and both are cracked. I am going to get new ones and replace them I am just curious as to if I need a new motor or just new manifolds. I took the oil cap on the top of the engine and saw this (see pics) and I checked the dipstick and saw a light colored oil. Do you think it was because of the exhaust leak or a cracked block or a blown head gasket? I am just wondering before I spend money to replace the manifolds if I need a new engine. I have a lead on a used engine, but if it was the exhaust manifolds then I will just replace and change the oil. Any advice anyone has will be greatly appreciated!

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I recently bought a boat from a buddy

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Nice buddy. The block is very likely cracked internally. Seal the water jacket and pressurize it then listen via the carb for air escaping into the block. use a bicycle innertube to pressurize it.
With engine removed check the stringers, floor, engine mount bases and the transom for rot.

Depends on how lucky you are. popping out a core plug is never good. drain the oil first and refill. .could have just been some moisture in the oil.
Did you check level and condition before starting?
Remove therm housing and thermostat. using a hose ,slowly fill the block to the top of the intake manifold and wait to see if it drops.
If dropping ,check dipstick for a rising level. Rising oil level is a cracked block.

Ayuh,..... How long did ya run it,..??

How much did the oil Level rise,..??

Like Guy said, drain the block, isolate the coolin' passages, 'n pressure test with air,....
If it's cracked, you'll hear the leak,....

V6 motors from what I have seen when not winterized properly DO crack internally.

So if this motor has that much damage externally and two (maybe more) core/freeze plugs popped out I would say the motor is toast!

So best thing to do is do a craigslist search for a complete V6 with manifolds and all..............

Sucks when this happens!! But it does!

I have a new 4BBL intake for this engine if you find that your intake cross over tube is rotted through.