I have on boat engines. A boat engine has water pumping through the block when in use so it gets flushed out. You won't get it all out when your season begins. Do you run antifreeze or just water racing? Peacocks in the block could help get it out better.
Rules require we run water and I do have petcocks in the block. RV junk is cheaper, not that it matters and it would flush out easier I’m guessing.
