That would be almost impossible to do. What do they say they are using?
Based on where you live, I am guessing you never boat in salt water. You will rust out before your block does.
Like Bruce said that will never work. If you are worried about internal corrosion of the block/heads and manifolds, then after manually draining you can fill the engine with -100 Marine antifreeze with corrosion inhibitors. I've done it for 15 years in salt water and the block is still not rusted out. It might not be necessary if in fresh water though.