If you have a pic how you hooked up the heater to the engine I'll be your best friend forever. Haha. Seriously though, I have the same engine and almost the same boat and will be hooking up the heater next week.
I have my boat at the storage yard so no pictures. I think what the dealer did was install a new housing over the thermastat that had an inlet and outlet fitting. The hoses were run up the port side of the boat to the heater core in the front storage compartment. If this thread continues for a few more days and I have a chance to get out to the boat I will take some pictures.