Somewhat ambiguous info regarding winterizing engine in Merc manual

[vetplus40]

I am still in the early stages of getting a handle on how I/O engine cooling works, but I ran into a bit of an interpretation issue with the manual for my 5.0 . The manual says the drain the block with the drain valve and add F, but does not specify how to do so.
I have watched a few videos and the common method (which I have used previously) seems to be to run the engine on muffs until the thermostat opens and then valve off water and valve in AF. I can see where this method might mix some residual water in the system with AF being added - thus diluting the mixture, but I cant see draining a hot block and then solely relying on muffs to refill the system with the the engine running.
Maybe the intent of the manual was to add AF via the hoses (without using muffs) but it certainly gave no direction whatsoever. Thoughts?

 

[alldodge]

common method (which I have used previously) seems to be to run the engine on muffs until the thermostat opens and then valve off water and valve in AF. I can see where this method might mix some residual water in the system with AF being added - thus diluting the mixture,

You are correct, this will dilute the AF and most certainly crack the block

Drain everything, coolers, block, mans, large lower water circulating hose, everything. Once drained your winterized, and if you want to use AF, disconnect hose at thermostat and fill from them. You can fill from muffs if desired,

 

[Bt Doctur]

The manual says the drain the block with the drain valve

Sounds like a quick-crack drain system .got to be careful with those. opening the drain should release about 4 gallons ,if not manifold and/or block drains are clogged

 

[thumpar]

Seems pretty clear. DRAIN block first. I don't know about your manual but the ones I have had say AF is optional but always DRAIN first. The AF is for corrosion protection only.

 

[tpenfield]

If you drain the block as indicated, then you should add AF to the cooling system WITHOUT running the engine. You may have to fill via the large recirculating pump hose up at the thermostat housing.

 

[Scott Danforth]

the manuals are mostly clear

drain the system. the proper manual goes thru the steps of how to drain your exact system, if its a manual single point drain, the air operated single point drain, the 3-point drain or other.

then it states optional addition of AF. and the manual clearly states to remove the thermostat housing or hose and fill the non-running engine until the block is full, then replace the thermostat housing.

since the OP is discussing what appears to be a single point or 3-point system, most likely manual 31

in manual 31, that is on page 1B-70
in manual 30, there is no option (HX cooled)
in manual 26, that is on page 1B-25
in manual 25, that is on page 1B-35
in manual 24, that is on page 1B-24 and 1B-41 (this note is a bit ambiguous as it simply says you can AF thru the motor during layup)
in manual 23, that is on page 1B-46 (this note is a bit ambiguous as it simply says you can AF thru the motor during layup)


if you dont have your factory manual, you can view them on-line via links in the stickies

http://boatinfo.no/lib/library.html