If its a half system, meaning only the block and heads have coolant in them, just pull bottom hose off of manifold and manifold and riser will drain. If its full system, meaning manifolds have coolant and sea water from heat exchanger dumps out through riser,you have to drain coolant out of entire system. 'nutcase
He's right- just drain it by removing the appropriate hoses. Try to catch the antifreeze if you can.
Hopefully the bolts won't be seized. Either way, put some penetrating oil on 'em a few minutes before you start.
drain the A/F from a manifold drain plug into a catch can,
drain the raw water in the riser by removing a drain plug.
Expect a minimal amount of water (a few drops if any)to enter the manifold, wont hurt.
