Draining block - Leave open or closed

[kvand347]

We winterize over 300 boats a year, We always drain and then flush with a marine, non toxic antifreeze. We leave the blocks dry and plugs out. In the spring, we simply summerize, install the plugs, test run, and deliver. We have not had a frozen engine ever doing this process. Al

Just curious as to why you drain the anti-freeze. I know other people do it as well, but the marine stuff is good to -50*. From what I've read, the marine stuff will not expand. Just seems like a waste of anti-freeze if you're just going to drain it. I'm open to anything though!

[cadunkle]

I normally drain water (pull all plugs), then run 4-5 gallons antifreeze through it after pulling thermostat, then pull all plugs again, clean bilge, remove all water, clean etc. and leave plugs out block drained until spring. Paranoid maybe but it makes me feel safe.

This year I think I'll be pushing past when we get freezing temps at night. What do I do with boat stored outside covered up? Not worry abotu a dip below freezing overnight and do nothing? Run it to temp at sunset and leave it to stay warm overnight? Drain block after every use? Drain block and pull all hoses for raw water pump and heater? I don't know? Don't want issues from freezing but being as I want to push this season it makes it difficult not having heated storage before I winterize.

[kvand347]

I normally drain water (pull all plugs), then run 4-5 gallons antifreeze through it after pulling thermostat, then pull all plugs again, clean bilge, remove all water, clean etc. and leave plugs out block drained until spring. Paranoid maybe but it makes me feel safe.

I guess I still don't understand why some people pull plugs after filling with anti-freeze?? Are you worried that it will freeze/expand? Just wondering because mine is sitting with antifreeze in it right now and was not planning on draining it. Aren't you asking for corrosion when draining the block and leaving it open since there is no anti-freezef left (over very little)?

This year I think I'll be pushing past when we get freezing temps at night. What do I do with boat stored outside covered up? Not worry abotu a dip below freezing overnight and do nothing? Run it to temp at sunset and leave it to stay warm overnight? Drain block after every use? Drain block and pull all hoses for raw water pump and heater? I don't know? Don't want issues from freezing but being as I want to push this season it makes it difficult not having heated storage before I winterize.

At minimum I would pull the block plugs. I figure a cracked block is more expensive than exhaust manifold/hoses...

I've heard some people will leave a space heater or tap light on in the engine bay...not sure how much a light bulb will do for warmth on a cold night. Space heater sounds dangerous with gas lines so close.

[wotan2525]

I normally drain water (pull all plugs), then run 4-5 gallons antifreeze through it after pulling thermostat, then pull all plugs again, clean bilge, remove all water, clean etc. and leave plugs out block drained until spring. Paranoid maybe but it makes me feel safe.

This year I think I'll be pushing past when we get freezing temps at night. What do I do with boat stored outside covered up? Not worry abotu a dip below freezing overnight and do nothing? Run it to temp at sunset and leave it to stay warm overnight? Drain block after every use? Drain block and pull all hoses for raw water pump and heater? I don't know? Don't want issues from freezing but being as I want to push this season it makes it difficult not having heated storage before I winterize.

I always figure that if it's not cold enough to freeze a pail of water solid, it's not cold enough to freeze your boat. That being said -- if you have electricity, a small 110v heater would be cheap insurance and keep it plenty cozy under that cover.

[beast 496]

The way we do winterize, with adding the extra 2 gallons of marine antifreeze and then letting it flush out the block and manifold, is a process that works for us. Just an extra amount of safety. Plus, we don't have to remove any hose fittings from oil coolers, the sea water pump is saturated in marine antifreeze, which lets the impellor be lubricated upon spring start up. Once we pull the drain plugs, we do not reinstall for running of the antifreeze.
If you want extra fall security without wanting to drain the block all the time, I suggest a block heater, basically you buy a block heater that will take the place of a core plug. This is the same type as optional equipment from GM. You can buy at most auto parts stores. This will keep the block over freezing conditions with the motor hatch down. In my Suburgan, it will keep the coolant warm to the touch even in the dead of winter. Al

[cadunkle]

I guess I still don't understand why some people pull plugs after filling with anti-freeze?? Are you worried that it will freeze/expand? Just wondering because mine is sitting with antifreeze in it right now and was not planning on draining it. Aren't you asking for corrosion when draining the block and leaving it open since there is no anti-freezef left (over very little)?

I use RV antifreeze which does not have the same corrosion inhibitors are regular automotive antifreeze. RV antifreeze will also freeze and turn to icy slush well before the rated temp at which is freezes solid, and it doesn't take much water mixed in to drastically reduce the freezing temp. I feel safer draining it all out after running it through, in that the RV antifreeze will be mixed with some water and most of that comes out. Without a block full of liquid and with drain plugs out there is room for any remaining water or antifreeze to expand without doing damage.

Call me paranoid, but I lost a SBC to freeze once. At least I suspect I did. I realized in spring I did not get all the water out. I had a busted leg from a motorcycle accident and had a friend do the winterizing. Poured it full of RV antifreeze and suspect it froze. Was fine first time out for a few hours but second time out that season it broke down and milkshake everywhere. My best guess is freeze did it... hence my paranoia about freeze damage and residual water.

[wotan2525]

I've been using RV antifreeze (and not draining it) for 10 years in northernish WI where we see an honest -25F every winter. Never had a problem. Everyone seems to have their own method, but I'm going to stick to mine.

[Salty87]

This year I think I'll be pushing past when we get freezing temps at night. What do I do with boat stored outside covered up? Not worry abotu a dip below freezing overnight and do nothing? Run it to temp at sunset and leave it to stay warm overnight? Drain block after every use? Drain block and pull all hoses for raw water pump and heater? I don't know? Don't want issues from freezing but being as I want to push this season it makes it difficult not having heated storage before I winterize.

depends on how warm it's been prior to the freeze, how cold it will get, and for how long it will be that cold. our engines are insulated very well. it takes some time for the cold to penetrate enough through the hull and engine cover to freeze fairly thick iron.

the early fall overnight freezes where temps start in the 50's or 60's and get back there as soon as the sun shines isn't a problem. you have to worry when the day isn't any warmer than 40's before the freeze and it won't warm back up for a while. in that case, there's been enough time for the ambient temp of the block to drop closer to the freezing range.

fill a jar or even plastic cup with some water. set it on the floor of your boat under the cover. check it first thing in the morning for ice. it has to be really cold for more than 8-10 hours to make ice.

disclaimer...i'm not advocating that any of you crazy northern dwellers not winterize, these are just observations from central tx where i haven't had to fully winterize every year. or, we'll get chances to take it out in Dec or Jan. Drain the exhaust (i have the ever-clogging petcocks), pull the lowest hose on the engine, run shower dry (do this first). then wait for good weather again.

[Blackntan90]

Well I winterized this past weekend, hated to do it so early,but lots of other stuff to do. Man am I glad I did it when I did- we have SNOW in the forecast for this coming weekend!

[docdrs]

After I drain my antifreeze I reinstall all plugs so then I'm ready to go in the spring. The knock sensor plug can be a real pita if left out. I left it out the first season and had to tap the block threads to get it back in in the spring due to the corrosion on the threads over the winter. If you leave them out I suggest you coat the the block threads with some anti seize or spray some fogging oil on them to prevent corrosion. Re installing with anti seize prevents any corrosion and seals up the lower block.