Yes, I read the other threads...

Seems like a lot of guys and non-binary's prefer to leave the thermostat in and run it up to temp @ 140 / 160. After the motor was rebuilt, I'm not sure what tsat is in it, but I'm guessing at OR under 160. Maybe it's just me, but what if it doesn't open right at that temp OR the thermostat doesn't open, which can happen. Isn't it easier/safer to just pull the t sat so you know it's pulling antifreeze into the block?

Last year I pulled the t stat, hooked up a sump pump in a bucket of antifreeze and fed it through the muffs. After 7 gal or so, it was a pretty solid AF color out of the headers and I shut the engine down considering it winterized. The engine was shortly pulled to be rebuilt, so it was a moot point whether or not it worked.

Are people too lazy to pull the t stat or is there another reason I'm missing? Second time winterizing so just trying to learn.

Thanks

Plenty of discussions on winterizing.

Typical Merc open cooling system…..

No reason to pull the tstat. It does’t sit directly on the intake manifold and close off anything- just reroutes back a bigger % to block when closed. We get as cold as -20f here. So, we are in deep freeze land. My ice in cove get’s over 30” thick.

Yeah we may get a few inches on top of the pools around here

Are you saying you think 7 gallons or so through the muffs is sufficient? Do you bring your temp up to open the t stat?

I totally drain. Block drains. Exhaust. Bottom recirc pump hose connection. Hose from sea water pump. Just as you woukd if you are like many marinas and winterize without antifreeze. Then put thru 5-6 gallons of an antifreeze mix concoction from bucket into muffs.

Hi, I used to work at a marina in upstate NY back in the late 90 and early 2000. Now I hobby in the boat repairs, winterizing the same way we had.
Run boat up to temperature and let thermostat cycle, then pump the antifreeze in. V6 or small block v8 we use 5 gallon of antifreeze, then BBC we use 7.

Usually stabilize fuel first, grease fittings, run it, then at the last gallon, spray fogging oil in the throttle body if you can.

DONE

hang a couple moisture bags in the cabin and engine compartment and cuddy, keeps the black mold that can sometimes appear at bay.

its not easy but we always drain all water it really helps get the scale and rust sediment out then we fill with non tox then wd40 the entire engine

I flush mine with water on the hose for a while to clear the brackish water from the last run, then drain the blocks and exhaust, then push 4 gallons of pink stuff into each engine.

i have always removed the t stat but if it.s not necassary it would make the job easier,sb,are you saying on a mercruiser 330 hp engine i can just warm it up until it hits operating temp and put the antifreeze in?

Following is not about engines with crossover systems.

tstats don’t sit in tstat boss on intake msnifold. They sit up in the merc tstat housing. When tstat is closed they prioritize .% of water back to block thru recirculating pump. When that is full (say block starts empty) then small % gets put to exhaust. When temp rises and tstat opens more goes out engine right to exhaust, less recirculates.

Either which way (cold or hot) - the engine gets filled first and then exhaust fills.

I think tstat pulling started happening when people filled engine with antifreeze from the top with engine off.

One of my personal boats, i pull outdrive each winter (various reasons including lubing ujoints/checking bellows/less chance if theft (it has an alphaSS and boat stored outside) I drain engine/hises/exhaust /etc) and i pump reg green antifreeze (corrosion protection aluminum heads and etc) and pump thru transom assembly with hose /remote bikge pump and a bucket under each tailpipe. I reclaim sll of it in spring. One drop doesn’t hit ground in filling nor reclaim. Here, boats can sit stored 10 months. Don’t need my aluminum being chowed by corrosion just sitting there.