On cleaning the block-
pull lower drain plugs AND the bilge pluge
pull one of the hoses on the tstat housing. run garden hose here S L O W L Y. . .
coat hanger, long zip ties, welding rod, etc thru the drain plugs until it runs clear.
OR the easy way...Remove lower drain plugs. Back trailer into water. Fire it up till it runs clear. pull trailer out. pull bilge plug. Consume boat soda.
I do this at the launch ramp at the end of the season.
Dan'l