purple stuff from home depot if you don't use gloves will take every bit of oil out of your skin burning it, I had big blue gloves man does that stuff work well takes a slight bit of scrubbing on some things but everything is degreased now
ok for folks following along this was my set up for steel and cast iron only as it will eat pistons if left in wash for more then say 1 hr.
1 vat of purple stuff for degreasing
1 vat of oxalic acid leaves a yellow dust after cooking off
1 vat of hi ph to neutralize after oxalic acid
1 vat of phosphoric acid
another hi ph neutralizer
gas grill large used at lowest temp to cook off without fearing warpage. this protects metal from hydrogen embrittlement due to hydrogen leeching into metal
as with any acid , must monitor parts closely to be sure they aren't cooking in the acids too long ruining parts.
after cleanup I soak them with wd40 to keep new rust at bay or primer to keep them rust free using metal etching primer.
the last good engine I did not do this process with because I tore down and found it just needs a valve job to remove rust , all cylinders did very well on compression test except I could tell the valves weren't seating properly due to contamination so I yanked head and cleaning up.
dropped oil pan as well and found same slime as all the other engines moisture must get encapsulated in the oil and turns into this sludge I highly recommend any engine you buy to drop oil pan and clean oil sump and pickup as a bear minimum before installing in boat. pics soon
good call.