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Just wondering what's the best way to go about it. Paint remover, soda/sand blast?
I am just a DIY non-pro looking after one old boat, so take this with a large dose of skepticism, but it seems to be working for me. Our engine was in the boat. I removed all the parts I could and took them into my home shop for close inspection, cleaning and painting. I sent a couple to a machine shop for professional cleaning (manifold).
- I scraped off the grease and flakes, using any hand tools that worked without damaging: flathead screwdriver, stainless wire brush, sharp pick, etc.
- I degreased with detergent, keeping it out of holes and away from parts that may be damaged by detergent; then rinsed with water.
- Continued scraping and brushing as much of the rust as possible. The ideal is to get to bare metal, but that's impossible working by hand at home with an old engine, so I did the best I could. My logic was that if remaining paint resisted removal, it must be adhering pretty good - pros would get down to bare metal.
- Emery cloth helps.
- I vacuumed and used a small air spray bottle from a computer store, to blast clear residue, being careful to keep it out of the inside of the engine.
- I stabilized a couple of rusty areas with a rust stabilizer. They chemically turn the rust to a hard black surface. I never did find one that appeared to excel above the others in googling the net, so finally just used a product at a local auto parts store. Pros would be more informed and methodical. I kept it away from bolt threads.
- Final wipe with acetone, keeping it away from rubber seals and other things that could break down. I wore protection for skin and lungs.
- I picked paints designed for engine heat. The 500 degree brands for all the parts except head and manifold, and the high-heat (1200 degree) brand for those.
- Regarding primer, I never did convince myself primer was necessary, but the pros use it. I checked the instructions that came with the paint brand I settled on (Duplicolor -- it was handy. Pros have preferences).
- I masked off bolts, threads, holes, rubber parts, spark plugs, etc with masking tape and kitchen aluminum foil, and draped a drop-cloth around the engine.
- I sprayed on three coats of paint, being careful to apply the next coat within the minimum/maximum time window in the instructions -- if wait too long, have to wait several days. I set up ventilation and wore a mask.
- Some paints require heat before they harden after drying. Pros do that in ovens, the rest of us let engine heat do it.
- I keep some paint on hand for touchups over time.
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