AND..... Closed cooling lets the engine operate at or closer too the temps it was designed for, thereby burning fuel more efficiently. Also, all the internals of the engine will see glycol which has rust inhibitors, as well as lubricates for the circ pump etc. IT ALSO keeps sand, shells, and other CRAPOLA out of the engine/manifolds, if full cooled.
It's also adds resale value!
I'm a HUGE believer in closed cooling, if you couldn't tell!
I buy and sell many, many boat, and I always convert over. Who wants to deal with winterizing and possibly having thousands of dollars of damage, just because you misjudged! Not to mention, just a pain in the arse!
If you leave out of the water, or in a no heat situation, you'll need to drain the coller, but no biggie.
One of the things, I like, is we can go down to the docks, fire up the twins and take off, whatever the outside temp!
But that's just me!
2002 Sea Ray 340 DA
1992 Maxum 2300SR