Water inside 43L OMC motor

"4.3L OMC. Overheated and then

"4.3L OMC. Overheated and then seized solid.

Removed all the plugs. Water came out of the front-right and rear-left cylinders (but probably due to crankshaft/piston positions.

So Removed the engine and stripped her down.

Found no cracks, head gasket looks good. Found faint black marks on the inlet manifold gaskets, between the water jacket and the inlet on the middle two cylinders. I think water bypassed into the inlet ports, then into the cylinders and then into the crankcase.

All of which caused the hydrolock

Is my theory plausible? Could both of the inlet manifold gaskets fail at the same time, If so why both sides at once? If I am right, this could be an inexpensive repair, new gaskets and rebuild....

Any comments.... Suggestions"

and the risers they look like

and the risers they look like what? These one piece risers and manifolds?

I had a riser gasket go on me

I had a riser gasket go on me on 1989 5L OMC...locked one side of the engine...would be pretty coincedental for both to go at same time but so would head gasket...riser gaskets are cheap I would replace them now anyway. What about con rods? how do you know they are ok? all pistons at least reaching TDC? any cylinders cracked? look for horizontal lines below normal wear line but will be jagged not straight.
Paul