Overheating damage? Help?

[rschap1]

Took the son and his buddy tubing a few days ago behind our Volvo v-6 deck boat (sorry not too fancy or fast).
Impeller gave up and temp pinned gage REAL quick.
Headed home asap, maybe 1/4 mile on water and a minute and 1/2...but it got hot. Smoke came off all the rubber coupler/connections on each side of the exhaust and those got toasted.
Yesterday I replaced the impeller and thought I was set until seeing how bad the exhaust rubber pieces melted. Pulled those and pick up new ones today. 4 hose pieces and 2 sets of "flappers" that go in the "Y" pipe. With open risers I wanted to ensure that my freshly installed impeller was pumping. Plenty of water, plenty of flow, but filling the cylinders also. Now I am REALLY hoping that the manifold to riser gasket just got cooked and are leaking. It takes all of about 20 seconds to lock the motor up tight. Center cylinders on both sides fill fastest and fullest. Each front is getting water but does not seem as bad.
Going to tear the risers off shortly, maybe exhaust manifolds, but...wondering what my odds are that heads aren't cracked, head gaskets didn't fail...Do not want to waste to much time if the entire motor is toast...any experiences, ideas, help, or anything else would be greatly appreciated. THANKS!!!!

[C35]

Most likely head gaskets. And if it's hydrolocking while running there's a good chance you bent some rods. Maybe not much, but you'll find out a few hours after you rebuild your top end and a bore or two loses compression. Hopefully it locked up while just on the hose. If not, you might roll the dice and get away with head gaskets- maybe heads. But depending on the engine age you might think about a reman.

[Ratickle]

Definitely not good.

[rschap1]

Well, I am buying lottery tickets
Tore the risers off and the bolts were pretty loose and gaskets looked bad.
Siphoned the water out of the manifolds, ran the motor over a lil' w/o plugs, shot some fogging oil in each cylinder, rolled over again, and went to replacing all the exhaust stuff that got cooked.
I should have explained better when the water got in the motor. After I got it home and was looking it over, I kept starting it for a few seconds, thinking I did not want it to seize as it cooled. All seemed fine except for I figured impeller was needed.
AFTER I replaced the impeller, it filled the cylinders. I tried to start it after installing impeller and pulled some hoses to see where the old rubber blades went and seeing if I did have water flow for sure. Starter would not do it, and I first thought it seized and tried turning with a ratchet on crank nut. SOLID. Pulled plugs and water...
My hopes came true when all that happened was the riser gaskets let water into the manifolds. I had kept seeing clean oil on the dipstick and liked that, but realized I had yet to run with an impeller AND warm enough to open the stat.
So at this point I clean the risers and manifold tops, installed new gaskets, replaced all the melted exhaust couplers, and t-stat gasket that I needed. Still worried that once stat opened and water pressure actually circulated through the motor, I was going to find worse. But my luck was good. I tightened the manifold to block bolts, those were loose and checked some other stuff over. Only issue I had was the starter dragging and even engaged once while the motor had been idling for a couple minutes...I replaced that this spring and the ignition switch after old starter melted from staying engaged for 5 minutes at start up. Checked new starter bolts and those were slightly loose too (?). Once I did that starter seems fine now. Then spent longer cleaning up the mess than the repairs took. Black melted rubber makes a heck of a mess. My bilge still has lots of flakes of melted powder coat or paint from the exhaust elbows, riser gasket scrappings, and crusty rubber remains. Did what I could to clean up. Ran around the lake for 10-15 minutes with son afterwards and then took wife and daughter around "pontoon" style for about an hour. Ran it hard for the last minute or 2 just to check it out again. All seems good, THANK GOODNESS
Appreciate all the help and suggestions. Sorry if I had included quite enough info or details initially. I had worst case scenarios running through my head rather than best. I got a few hundred dollars and a couple afternoon into now. Hopefully set for a while
THANKS!