Got a bit more done today and unfortunately discovered the engine is seized
oh well, I bought the boat assuming it would need a swap, frustrating thing is the person before has definitely been wrenching on it and it would've saved me a bit of time had he just been honest about it..
I pulled the raw water pump and the thermostat housing and found the same heavy corrosion I found in the water jacket at the freeze plugs.. Is this typical or was this boat in acid? I knew the impeller would be shot and it was of course, little pieces of it missing but the impeller housing seems fine, spins tight and freely - can't think of any way to test the seal though..
My big concerns now are what will be salvagable.. the intake manifold is very corroded where I pulled the thermostat housing. I'm afraid I'll find the same thing in the exhaust manifolds - should I be concerned here? Can these be dipped or something to restore the interior areas? Swapping the intake wouldn't be so bad - could easily get an aftermarket or something.. Here's some pics: