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Oxidation / White Rust

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Sam110

Regular Contributor
I recently acquired a '73 Evinrude 18 hp that was seized and said to have been stored under a porch for who knows how long. I did get it moving again and believe it is worth trying to save. The main issue I have at present is the amount of Oxidation or White Rust that exists on at least half of the power head and lower cowling. It doesn't appear to be the result of salt water use as I've pulled the head to get things moving and the water jacket appears to be normal/clean. This condition limited to everything within the engine cover.

Is there a method of dissolving / removing this white substance short of bead blasting, or a chemical bath that would not require complete disassembly? A wire brush works on areas that can be reached but thats minimal. I've searched around on YouTube and it seems that Hydrochloric / Muriatic acid works but not sure I should chance using such chemicals on assembled motor. Anyone have any luck removing this stuff?
 
Spray it with WD40 let it soak a bit and blast it with the hose. Then take the connectors apart and clean with electrical cleaner and let thoroughly dry then put the connectors back together with doelectric grease. Pull the grounds apart and lightly sand metal to metal.
 
Rust / corrosion on steel is iron oxide and brown-----------Corrosion on aluminum is aluminum oxide and is a white powder.------Some will argue but a motor that was seized may require a teardown.-----At least remove the bypass covers for a peek inside the engine.
 
Here's a couple pics of the 'crud'.
 

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Mice were in there.---Have a few " freebies " like that myself.-----Typical thermostat in the " failed open " condition too.
 
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Could be right, I'm sure the guy who I bought it from had chased them out before he sold it to me. I didn't see any signs of a nest. Seem's your right about it being oxidized as it is all white and only seems to be on the aluminum parts. Piston sleeves had a film of rust and I considered pulling it, separating it and honing the sleeves but ...???

Kim, I do like your suggestion of how to deal with it. I wasn't too 'keen' on using the hose on it but I believe I'll pull the gear case out first and use a power washer as soon as it warms up a bit.
 
There are lots of things you can do to beautify that motor.-----But first get it running before you attack the cosmetics.--------Then if you use water in the cleaning process you can start it up in case water gets inside the motor to dry it out.------Water inside fine machinery is a NO,NO as you know.
 
Agreed ! Reminds me of when I took a vehicle differential to an acquaintance who was an Auto Mech. Teacher at our local HS as asked if he could "set up" a set of new gears for me. He agreed but some time later I stopped by to get an update and there sat my axle housing outside his garage door, face up over a plastic pan half full of water from recent rains and everything was covered in a film of rust. I about ****!
 
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