Marine specific blocks as far as I have been able to gather from the so called "experts". True or not , I couldn't positively say.
A marine engine holds water only running and pressurized by the pump, shut it down and it drains off like a leaky radiator. If they are winterized , you drain out all the water from pet-cocks on the side ,the hoses get disconnected and dumped ,pet cocks on the exhaust manifolds drain them. Anything left gets diluted with a RV antifreeze.
A boat you could get an engine from ,means no one cared anymore and chances are it wasn't winterized.
If he wants to save the 340 ,getting it sonic checked for core shift is a smart plan.
Best way to winterize an inboard is to pull off the hull intake hose and stick it into a bucket of RV antifreeze then start and run until you see the antifreeze out of the exhaust..
If you have a hot water hose (for wet suits) or heater, these need to be addressed separately....
