351w winterization and thermostat HELP

[h2o.skier85]

So as long as I've owned my boat I've always put antifreeze through it as part of my winterization routine and have never had any problems. I do this by running it through a fake a lake after the engine is nice and warmed up. However, a marine mechanic recently told me that I've been doing it all wrong. He said that as soon as the cold antifreeze hits the thermostat it will close and only send antifreeze into the manifolds. Therefore to get antifreeze into the block you have to drain the block, remove the hoses from thermostat, and then pour antifreeze down those hoses (to bypass the thermostat). Is this correct? I had never heard of this before.

[MattP]

@E_T How did you do your 351w this winter?

[oldjeep]

Draining and then pouring the antifreeze into the hose that leads to the engine water pump is certainly the safest way and the way I do it on my Monsoon 350. Also if you have a heater make sure to blow those lines out and then pour antifreeze in them.

 

Lots of people use the fake a lake method - seems messy and a pain in the rear to me since that means I would have to winterize outside rather than in the comfort of the garage.

[E_T]

Never heard of it closing. You could always heat the antifreeze to prevent this

[wolfgang]

I always remove the hoses and fill them with RV antifreeze...... After draining the block and heater. 15 successful years in Ontario outdoor storage

[rfa]

legitimate debate about the "best " or safest method...however, regarding the cold antifreeze closing the thermostat...unless you're running hot water through the fake-o-lake, why would the cold antifreeze be any different than the cold water??? I have retrofitted a "T" before the raw water pump on my last 3 boats (same as, but more convenient than a fake-o-lake) and no problems over 20 years in the MA winters. I do agree that the manual draining and refilling is ultimately the surest way to be safe.

[Jordan]

if the engine is warmed up to full temp when you start drawing the antifreeze, it will be just fine....the pellet on the t-stat in on the engine side. The introduction of the antifreeze won't instantly close the thermostat.

 

If you are worried about it....remove the t-stat before winterizing.

[blagrata]

My thoughts:

 

1) You must drain the block, manifolds and hoses of water... period.

 

2) If you don't drain the block then you are really taking a risk if you just run antifreeze in via the raw water intake. Even if the engine is at operating temp.... you're going to get a mixture in there... not pure antifreeze. My manual doesn't even mention antifreeze... just draining. I've always been a little timid of just doing that... and add antifreeze. In theory though if you get the water out... air freezes at like -400 right?

 

3) If the block is drained.... when you start the engine the block will fill (with either antifreeze or water... whichever is provided). I believe this to be true regardless of the thermostat. I have never been able to find a good picture of why this should be so... but think of it this way.... if the t-stat has to get to 160 (or whatever) to open... and there's no water in the engine block circulating... how's the t-stat ever going to get to 160? I can't happen by induction of the metal to the metal.... the engine would be cooked long before that.

 

4) Personally I drain the block and all the hoses.... then I pour antifreeze in via my heater hose port (I have an Indmar monsoon). I believe this would do the same thing as removing the t-stat... and is less involved. I do also pour antifreeze in the hose for the raw water intake so it runs into the v-drive (forgive me) and transmission cooler. Then I pour antifreeze into the heater hose (after it is blown out with a tube air pump... again.. forgive me). I have never poured antifreeze into the exhaust manifolds... couldn't figure out a decent way to do that without making a mess. Just have faith that they're full of air.

[blagrata]

One year I did put everything back together after draining and then stuck the raw water intake hose in a 5 gallon bucket of antifreeze. Sucked it all up quite nicely. Verified pink stuff in block by opening one of the drain plugs. Again... my only experience has been with the Indmar Monsoon.

[lff]

Question from someone who has always lived in FL: if you are draining all the water out of the engine why put antifreeze in?

[jstaab3]

@lff exactly right!!!

[Zman]

Some would say adding antifreeze after draining the block will prevent the cooling water passages inside your block from rusting during long winter lay ups. Remember, antifreeze has rust inhibitors.

[blagrata]

@Iff That is a hotly debated topic (antifreeze or no) that I have read many threads on.

1) The anti-antifreeze crowd says... air freezes at -360 degrees. If there's only air in the engine.. why do you need antifreeze. That does presume that you get all of the water out and there is none pooling anywhere... which I guess in theory if it doesn't create pressure when it freezes... who cares.

 

2) The pro-antifreeze crowd (even with draining) says.... what if i didn't get all the water out? It helps inhibit rust. It just makes me feel better. What harm does it do? Probably no harm if you use the pink stuff... and personally I try to drain as much out of the system and throw it away in the spring as opposed to just letting it drain in the lake or sewer.

 

There are several dealers that use the drain and fill with antifreeze method... at least I hope they're draining. Maybe they do it just to make the clients feel better.

[oldjeep]

Corrosion is why I add antifreeze after draining, especially the heater core since they are thin and rot easily.

[EFW]

I've used windshield washer fluid for 23 yrs in the same engine . No problems. Buffalo NY winters.

Whatever floats your boat.

[MISkier]

I am really confused by this thread. I always thought the thermostat let water out of the block. That is, the water pump pushed water into the block and also circulated it through the block until the thermostat opened and let the water pump push new, colder water through the block by allowing the hot water to escape the block and exit the manifolds. Seems odd to have something designed to prevent water from entering the block in the first place. I always thought the thermostat held the water in the block until it was hot enough to open and allow it to be replaced/cycled out.

[adkh2oskier]

@h2o.skier85 I winterized my 1989 CC basically the way you are doing it. It has worked for the past 23 yrs through the coldest area in NY, the central Adirondacks. Last winter was especially cold, at one stretch from early January til early March we had 47 nights with below zero readings. No problems come spring. I was given the winterization method by the Nautique dealer who sold the boat.

[DW]

Just because the thermostat is closed does not necessarily mean a fluid won't enter the intake manifold and block. Look at the housing to see the bypass circuit setup to determine whether the thermostat condition actually makes a difference. Also, many stats have a bleed allowing fluid to pass through to the intake manifold. You can also look at the circuit and find an alternate entry point, perhaps the heater core hose to the intake manifold which usually comes from just prior to the thermostat and you can kill two birds with one stone on that one (fill the heater core and the engine via the same port).

[Mastercraft81SnS]

There are many different ways to winterize a boat and everyone has an opinion too. The mechanic could be trying to get you to pay him to winterize your boat;). The boat we have is a 1981 MC and we do it about the same way as you and it has been done that way sense it was bought. It was the way the dealer said to do it.

[GAJ0004]

I have the 351block on my 94 Nautique. I drain the block and the manifolds. I draw the RV antifreeze out of a bucket. I use about 3 gallons. I disconnect the hose at the base of the transmission cooler and fill the engine while I am fogging it. The antifreeze is mainly for corrosion protection. If I was a snowbird I would do the same with my boat in the south if I left it storage while up north.

[h2o.skier85]

Thanks everyone! Just curious but should I be doing anything to transmission cooler? If I disconnect the hose at the base of the trans cooler when running the antifreeze through the engine/manifolds, isn't there still water left in the trans cooler that could freeze?

[TallSkinnyGuy]

My understanding on my boat is that disconnecting the hose at the base of the tranny cooler allows all the water to drain out. At least I have never seen any advice to do anything different to remove excess water from the tranny cooler, so I assume that is the case.

[GAJ0004]

@H2o.skier85, if you disconnect the hose at the bottom of the transmission cooler it should drain out on the 351 engine.

[Mick04]

@h2o.skier85, I had the same concerns with my 93 Mastercraft (351W 285HO). I would disconnect the hose at the output of the tranny cooler, insert garden hose and idle until up to temp. I would then remove hose and pour 4-5 gallons of antifreeze in as the engine idled. I found that after reconnecting the hose, as the engine cooled, anti freeze would seep backwards through the system, through the tranny cooler, and even fill the water strainer. I never had a problem in 15 years of New England winters.

[A_B]

So if I am following the marine mechanic logic, as soon as the cold water hits the thermostat it closes, wouldn't it never open once the motor reaches 175 degree operating temperature, unless you are running in 175 degree water.

 

I have warmed my engines up since 1978, then sucked antifreeze through them. In NW Ohio, we get below zero often in winter. Way back when I first did this, I pulled an engine drain plug to check to see if antifreeze came out, it did. I don't think the thermostat immediately closes when cold water hits it, the water in your block is hot and will add cool incoming water with it and send back into the block. Unless the temp immediately drops, which I have NEVER seen happen.

 

The site below is a really cool moving diagram on how an inboard motor is cooled. Note that you can open and close the thermostat and watch the water flow. When the thermostat is cooled, your mechanic is correct in that the water is sent to the headers and out the exhaust, but also note the yellow arrows going into the block and back into circulation (closed loop) until the thermostat opens up, then it pulls in cool incoming water and mixes with the hot engine block water.

 

http://www.boatinghowto.com/content/how-boat-cooling-systems-work-240/

 

You can always run it on fake a lake and open a plug to see if any antifreeze is present.

[LeonL]

The theory of thermostats is that once it reaches temp it opens. It doesn't stay open however. It's constantly going back and forth, open to close, in an effort to maintain the temp rating of the thermostat.