Cleaning exhaust risers and manifold.

[VicB]

I have pulled my exhaust manifold and risers from my crusader 454. Water passages are rusty, but will clean up well. Exhaust ports have a lot of scale and build up from recent valve stem seal failures. What’s the best way to clean them up? Thanks in advance,

Vic

[bud37]

Heh Vic....are you talking about the exhaust ports in the heads ? What color is this residue....if black can you just wipe it out by hand/ scrape . A little bit on the port walls will burn out over time though, IMO it won't bother engine performance unless really plugged/ restricted.

[VicB]

Both my engines are raw water cooled. My valve stem seals got cracks in them (I guess from being 30 years old) and was letting oil seep down on the pistons and out the exhaust port. We replaced them when I winterized the boat last year. Fast forward this year, each engine has some amount of steam coming out the exhaust, making me wonder if I had a cooling issue. The port engine had about half the vanes missing on the water pump impeller. I thought that might be the reason. Not enough water flow and by the time it got to the exhaust it wasn’t enough to keep it cool. Replaced the impeller, collected all the vanes and still had some steam. I pulled the exhaust manifolds and risers and brought them home thinking they may be clogged. Very good shape for their age. Mostly what I see is in the dry side. Looks like hardened oil sludge from the stem seals and maybe just normal use. Wet side is brown from rust, but hardly any scale at all. I pressure washed them today and was planning on soaking them in one part phosphoric acid to 4 parts water (basically Barnacle Buster). Just seeing if anybody has had this experience.