to help answer any questions about -50 and -100 rv anti-freeze,as per an email I got answered from splash when I ask them a question last month.-50 will freeze at appx 7-9 degrees and expand only at -50 and below,-100 will freeze at 5-7 degrees and expand at -100 and lower.expansion causes the damage Not freezing.but you do have to drain all water and not dilute it when you flush,hope this helps,and it is against the law to use green anti-freeze at lake of the Ozarks,happy winter

Ive never had any of my vehicles crack a block, radiator , or anything using regular automotive antifreeze/water. Goes for my liquid cooled snowmobiles as well.

I have seen cracked engine blocks, split oil coolers, and freeze plugs popped out of boat engines, using the pink stuff over the years.

When i stored my boat in a building that really never got below freezing , because of its insulation, i simply ran the engines until pink came out the exhaust , without draining the strainers or coolers. I was playing with fire. I wouldnt do that where my boat may be sitting outside or in a building that gets below freezing and stays there for months.
The pink stuff will work fine, just be sure you have all the water properly drained before running it thru. When the water stops dripping from the block drains , dont assume its all out. It doesnt take much to clog block drains. Dilute it with any water and theres a good chance youll crack something. Happens all the time. Cast iron doesnt flex well.

Also, dont forget to drain the sea strainers, bellhousing coolers, sea water pumps, and about everything that may trap water.

joe,im not sure i agree with the playing with fire thing.you have no thermostat so if you introduce the pink rv af into your strainer and run 7 gallons through the system you have removed all the water.correct me if my thinking is not correct.

Id feel alot safer doing that after draining all the water out of everything, then doing that. This way the pink stuff isnt swishing around with several gallons of lake water in the blocks and coolers

So glad I live in AZ! I just cringe at the stories here of cracked blocks and such. However you guys have seasons.. But I don't miss the snow one bit! Good info in this thread.

by draining the blocks and making sure there is no sand/crap in the water jacket you will ensure there is not any captive water that will freeze and crack. I have seen where an engine had pink run through it but there was a pocket of sand in the block and that is where it froze...

i guess i have been doing it wrong for almost 40 years.:readinghelp:

Do you drain the engines and headers first or just run the pink stuff thru till comes out exhaust ?

After my test last year of the pink stuff with 20% water frozen like a concrete block at -10 deg, scared me !

the headers have drains but there is no getting inbetween the engines to pull drain plugs.as you know joe it,s really tight under my hatch.guess i could remove the center headers to do it.

Drain it all, then run the pink thru it, THEN drain it all again.