Why is this plumbed this way?
 

I am working on getting this Superboat going. I have a really bad boat problem. When I bought the boat I new the engine had taken in water and needed to be replaced/rebuilt. The owner said the boat overheated and cut out. His mechanic said the engine overheated and caused the exhaust manifolds leaked water in. I am in the process of removing the engine now.
I have never seen water routed this way? I have always plumbed incoming water to a crossover in the block then the water circulates through the block to water outlet/thermostat housing and then to exhaust manifolds. As you can see in the photo incoming raw water goes to a "T" in the block which then goes to the water outlet? To me this wouldn't pass water through the block necessarily? All may be diverted to exhaust manifolds?
https://cimg8.ibsrv.net/gimg/www.off...898d74d59.jpeg

Plumb it the way you think it should be done. That mess is much more complicated than it needs to be.

Thats my opinion.

Whatever that puzzle is it appearantly didn`t work so well . I agree with Tom , rip it all out and start fresh

Thanks guys not sure what was going on there. I will redo the tried and true way.

https://cimg6.ibsrv.net/gimg/www.off...0f491165cc.jpg
I guess the water system did work. The cylinders got a lot of water.

I didn't know marine engines were using water injection now too!

Ouch!

Gaskets installed upside down or wrong gasket?

I don’t know that it was the head gasket? Do you see something?
On the forensic examination the raw water pump plastic body had a section missing so I think it overheated. Both banks had the same water in them so I don’t think it was an exhaust manifold because I don’t think 2 would fail at one time. I think water got sucked back into the engine from the exhaust. Flappers not working.

ouch... serious mess here !
needs serious doctor to fix this ...

https://cimg5.ibsrv.net/gimg/www.off...1dca10cce.jpeg
not saying this is your problem, but it is a problem

noticed that too...

To answer the opening question, click here:
https://www.cpperformance.com/p-7395...for-chevy.aspx

and after reading that, click on the installation instructions on that page.

And there you have it. :)

Thanks for the replies, Good find SB makes sense now. Yes didn't even really notice the head gasket not lining up with that water port.
It is a different build. It has 990 GM heads, flat tappet hydraulic cam, 445 block, almost like old school LS7. The numbers on the block say that it could be either 2 or 4 bold main. It has pistons with big domes. I still dont have it pulled because my little tractor won't quite lift over the transom.
I cleaned the cylinders up a bit and surpisingly they look good. I thought for sure it would be trash. I plan to pull the rest and check out what I've got on the bottom end and go from there. I may rebuild a 496 or start from new. The bore is crudely measured at 4.250 with calipers,

https://cimg8.ibsrv.net/gimg/www.off...afa2cbeed.jpeg
https://cimg9.ibsrv.net/gimg/www.off...2f8bc8d6b.jpeg
https://cimg0.ibsrv.net/gimg/www.off...790851cb8.jpeg
Got it all disassembled and ready to go to a machine shop. I am going to do a 496 rotating assembly. I haven’t decided whether to use the 990 heads or go with some aluminum ones. I’m going to go to a roller cam though for sure.

stand that crank up when not in the block.........:D