Soaked engine first aid
 

I got snookered on a low hour (101) boat. Showed signs of rust on motor mounts and starter but could not see any other evidence.I found that the float switch was defective and surmize that the bilge filled up at some time. The question now is for all those racers that have dunked their motors. How do you treat the cast iron block and motor? I have removed the engine and pulled the pan and it looks good inside. No sign of water getting in but the block and oil pan look rusty and everything outside looks rusty. Any treatment for the cast iron ? I am replacing the oil pan

Hours don't really matter with rust, how old is the boat? It might not have been dunked. I have a 20 year old fresh water never dunked boat and the original block, starter, engine mounts, oil pan had rust. Where are you and where is the boat from? If your in a salt water environment, even if salt water never touches anything there is a lot of salt in the air (steel doesn't like salt in any form). The only thing you can do is pull everything out and do the 3 P's (prep, prime, and paint) but eventually everything will wear down and rust will begin again.

Wire brush and paint black. Black makes for easy touchups also.

I would use a chemical bath to clean the rust, otherwise your wasting your time. I use a product that is basically Phosphoric acid. Cleans metal chemically, turns rusty steel to shiny. I use it mostly on body work, wire wheel first with heavy duty wire wheel then wash with acid. Make sure you have full face shield and protective clothing when using a wire wheel on a 4.5" grinder. I had a wheel let go of some wires, I looked like I lost a battle with a porcupine.

Thanks guys. Really looking for racers who dunk their engines. I am a long time boater in Florida Salt so I am familiar with normal rust. I have treated it with "Salt away", brushed it with a Phosphoric acid rust product and painted it with an anti rust paint. When people refer to "Pickeling" their engine, what are they using ?

OOPs ! the boat was 7 years old. I just sold my '88 Donzi that lived in the same area for 23 years and didn't look this bad. Finding the faulty float switch and water insidde the starter was the smoking gun for me.

Pull the plugs and turn the engine over by hand to make sure there is no water stuck in the intake behind a closed valve.

If you get it right after it comes out of the water, the racer first aid is to tear down what you can, get the electrics off of it, and toss the whole block in a 55 gal barrel of diesel fuel. That should stave off the rust until you can get it home and tear everything down.

If you've had water in the block, it will probably be a slim chance that much of the internals are saveable unless it was pickled right away.

Soaked engine first aid
 

I don't know why I didn't think of it first, but researching cast iron corrosion, I found what the pros are doing for artifact preservation. The Conservation Research Lab for Nautical Archaeology has in depth studies on the process of corrosion of cast iron and metals in salt water. Basic is getting rid of the Chlorides first, loose scale and then treating the iron with a rust reformer. Sealing it off is last. They found that Tanic acid worked better than phoshoric for the rust but you must neutralize the cholrides or the rest is window dressing. They give several alternative methods including electroloysis.
The only thing that I had ever heard from racers was to get it out of the salt water and into fresh water, then deal with it.

Update: It is now more than 6 months since I attempted to stop or control the rust from my motor being subjected to immersion. So far it all looks good but I did have to follow up with some Epoxy paint on the motor mounts. These were the first parts that I experimented with.?? Rest is holding up so far.
Thanks for all the suggestions.