start with a truck motor (all you need is the block and heads) pull the heads and install stainless head gaskets (felpro marine thru summit racing is the least expensive). then replace all your core plugs with brass (about $30 from local auto parts store) Then transfer the water pump, starter, alternator, brackets, intake and carb from your existing motor
buy new manifolds and risers.
your AQ310 has a hotter cam than the standard 5.7 liter marine motor (and the truck motor), so you may want to transfer the cam as well.
yes, many places will offer replacment engines. if you have a DP drive, I would suggest buiilding a stroker. rebuilding the 350 is about $1500, a stroker is about $500 more.
plenty of posts on removing the motor. start by disconnecting the battery and the cables to the starter and block, then disconnect the trapezoidal shapped electrical plug (rubber boot with zip tie), disconnect the battery cables, disconnect the fuel line. unclip the throttle line, remove your drive, then remove the clamp ring securing the PDS housing to the transom plate then unbolt the 4 lag bolts holding front mounts to stringers, disconnect the hose from the power steering cooler to the raw water pump. lift up slightly, move motor forward about 6" to clear transom plate, then lift up.
however water in cylider is most likely a failed exhaust manifold. pull the manifolds, and inspect.
