Closed cooling winterize

[FriDaz293]

I just got the boat a couple of months ago and I'm winterizing my twin 5.7 mercruiser engines. They are closed cooling and when I went to drain the exhaust risers and heat exchangers. When I open the valves on the bottom of the risers that coolant was coming out. From what I've read is that fresh water still should be cooling the exhaust. Any help will be appreciated.

[bruceb58]

All depends if its a half system or a full system. A full system uses engine coolant to cool the block as well as the manifolds. In the case of a full system, the riser should have a raw water hose going to it to cool the exhaust as it exits the riser. With a full system, you really only need to drain the heat exchanger and possibly the hose going to and from the raw water pump.

[bruceb58]

I am sure this isn't your system but it will be similar.

https://inetmarine.com/sk4821freshwatercoolingkit.aspx

The top hose going to the riser should have raw water and the lower hose going to the manifold will be coolant.

Its good that you have a full system if the boat is used in salt water. Saves replacing the manifolds on a regular basis. If this boat is used in slat water, you will still have to change out risers occasionally. I am going to guess since you live in TN, you aren't likely going to be using it in salt.

[FriDaz293]

Thanks for the help. Yea my turns out it's a full closed and I will be draining the heat exchangers this weekend. Yea the boat has been in fresh water here in tennessee all it's life.