We extend to you a cordial "WELCOME ABOARD !" Come on in, make yourself at home, we are a friendly group of enthusiasts, and we also appreciate the classic Chris Craft Roamer, Corsair, and Lancer boats too , as they are all on the same family tree and share much in common !
I tried to (many times) indicate the need for care on this sort of thing and it sure is well worth it to raise the caution again. For the very reason you mentioned, I ran my antifreeze through the motor on three occasions, knowing there is some degree of flow through that t-stat whether it's open or not. The fluid I put away was run through enough times to be fairly warm, undoubtedly heated by the exhaust gasses, but also the warmed up block too.
Your comment about pulling off the thermostat housing, remove the thermostat and place a large funnel in the opening and pour in the antifreeze to assure the coolant reaches the block is a good idea.