The "pile of rust" I'm referring to is the engine, not the outdrive. The block, manifolds, and risers are still cast iron, so they are most definitely not "rust proof." The Ocean Series has some extra coatings on the cast iron, but those will only delay the inevitable. Closed or "freshwater" cooling is a very, very Good Thing. This is the single-most effective anti-rust step you can take with an I/O. Starter, oil pan, and risers can be replaced fairly easily. External rust on the block itself is mostly just cosmetic. If you find any, just wire-brush it clean and give it a shot of Rustoleum.

Make sure you analyze the "drain pattern" of the back of the boat, and add gutters, shields, etc. to any places where topside water drips or drains onto the engine. The bilge obviously is going to get wet, but if there is an automatic bilge pump at the lowest point, you can keep the water level down. Whenever I think of it, I pop the engine cover immediately after an outing and check for any water sitting on the manifolds, distributor, EFI, or anywhere else that ought not be wet. When cleaning up the boat after use, I flood the entire back area with the hose, to move any salt down through the bilge and out the plug. With the boat back in the garage, I prop open the transom cover and motorbox and let it all air out until the next trip.

Yes, the composite outdrive case is quite The Bomb, to be sure. I would think that there is enough years of use on these to declare victory.