Cleaning out cooling system on aluminum outboards

[zul8tr]

This is for a 1973 25ss engine I am working for some PM. Any recommendations on cleaning the coating that builds up on the cooling system aluminum surfaces around the cylinderes and adjacent areas. I have done easy to reach areas with a fine wire wheel on a variable speed drill and plan on getting a pencil shaped wire on the drill for other harder to reach areas. But is there a better way to get at the hard to reach areas, like a liquid cleaner of some type? A friend mentioned Corrosion X spray.

[88workcar]

I use muratic acid. It turns yellow and bubbles all over, smokes too. The you rinse it off with water.

[zul8tr]

I use muratic acid. It turns yellow and bubbles all over, smokes too. The you rinse it off with water.

Full strength or dilute (how much?) from the bottle the pool store sells?
I will test a small area.

[88workcar]

I get it at ace hardware, full strength. I do the blocks too if they are bad. It is easy to use and works wonders.

[David Mason]

In the Pro Division (Alky) it is the method used to clean the aluminum from the cyl walls. Used a swab and dipped it in the Muratic Acid and swab the cylinder while Dad changed out the piston. Once you did a few it was a 5 minute job.

Bought at local hardware store. I think even Lowes sells it.

[zul8tr]

I used the Muratic acid and it did a nice job, thanks for the tip.

Is there any protective coating recommended to seal the alum that will not effect the cooling heat transfer?