Winterizing a Closed Cooling System

[Horigan]

I have recently acquired 1995 Chris Craft 21 Concept with a Ford 5.0 EFI engine (50FAPHUE) with a closed water system. I'm not sure if the closed system was stock or added later. The provided OMC pamphlet manual talks about removing drain plugs on the block and exhaust manifold on both sides of the engine to winterize it. When I look at my OMC shop manuals, as well as the Seloc and Clymer manuals, they don't go in to specifics on how to winterize a closed system. The Boatinfo online OMC manual does show water flow diagrams for the closed system and it indicates the raw water does not flow through the block, but it does flow through the oil coolers and exhaust manifolds.

Can anyone confirm that I only need to open the drains in the exhaust manifolds, as well as drain the hoses to the raw water pump and blow the coolers out, to winterize this closed system?

Thanks in advance.

Rich

 

[Scott Danforth]

is this a full system or a half system?

Change oil and filter, change gear oil, then drain the raw water side

generally, with a half system (block and heads only), you drain the raw water line (and any coolers in it), pull heat exchanger end covers off, clean out debris, then reinstall covers, and then drain the manifolds (poking a wire or screw around to make sure the sediment in the manifolds comes out.

with a full sytem (block, heads, and exhaust manifolds), you drain the raw water line (and any coolers in it), pull heat exchanger end covers off, clean out debris, then reinstall covers.

 

[Horigan]

Hmmmm. Good question. I don't know the definitions of full or half system. If the difference is whether the exhaust manifolds are cooled by raw water or not, it looks like a half system. Good point on draining/cleaning the heat exchanger either way.

Here's a link to the flow diagram, on the right side. Is this considered a half or full system?

 

[Horigan]

The link didn't work. Attached is the flow diagram.

Thanks again.
Rich

 

[tpenfield]

Looks like a half system according to the diagram. If the boat/engine are new-to-you, you may want to drain down the closed portion of the system, or at least determine if the coolant in the closed side is antifreeze coolant of sufficient concentration (same as a car).

You would drain the raw water side, including the exhaust manifolds, heat exchanger, sea water pump etc.

 

[Horigan]

Excellent. That's what I was thinking, besides adding the exchanger.

Thank you.

Rich