Don't turn your
engine over if the cylinders are full of water as it is hydraulicked and will bend a con rod if you try and force it. If your anti syphon valve was the cause and you have fixed the fault, remove the injectors, spin the
motor over on the starter until
all the water is out of your cylinders, check the sump and if there's no water, replace the injectors and start the
motor, if there's water in the sump, change the
oil and filter before starting.
Monitor the engine while in the marina, if all OK think of modifying the anti syphon to prevent it re-ocurring. Yes both the head and/or motor can be lightly skimmed. For
Volvo parts cheaper than
Volvo marine(gasket sets etc). try Volspec.co uk For future reference try and find what else your Volvo base engine is fitted too, maybe a small excavator,tractor or similar then look around for an independant
parts supplier and you will find non marination parts much much cheaper
Hope this helps.