Please clarify Mercruiser 454 open system thermostat operation

[amanphoto]

Hi all,

I am in the process of winterizing my Mercruiser engine. I am a little fizzy on how the open cooling system (raw water through the entire engine) works. Specifically the thermostat. The question is, will the thermostat allow antifreeze to flow though the bock even though the engine is not up to temperature?

This is for future reference...

This year, I pulled all the blue drain plugs (5 of them) on the engine and removed the radiator hose filled the block with antifreeze.

I was looking for a simpler way.

Thanks.

[bud37]

The thermostat keeps the water, in this case, in the block and only allows it to leave ( and be replaced with cool water ) when the temp gets to the thermostat spec....unless there is a very small hole drilled to allow trapped air to escape. So if the block is drained then it will fill to the thermostat and circulate via the engine water pump.That is how I see it for the engine side anyways.....

[buster53]

Keep it simple...
Pull the T-stat out first, then run the engine and suck 3 gallons of AF thru. Done.

[Viper]

You don't need to remove the t-stat or warm up the engine first. Drain the block, hoses, manifolds, etc. then run the engine to draw in the antifreeze. The block will fill up. I've never warmed up an engine first because I won't winterize a boat that's still in the water just for reasons I've experienced from doing them in the water in the past. I've also never removed a t-stat to winterize. If in doubt, after you're done, pull a block plug and you'll see antifreeze come out.

[buster53]

So how long does it take you to drain the block, hoses, manifolds, etc?
My way can't be easier. Take out the T-stat, turn on the engine and suck 3 gallons of AF in and done.
And that's for a raw water cooled engine. Fresh water cooled? Same procedure except you don't even need to remove the T-stat.

[Viper]

Source of the post So how long does it take you to drain the block, hoses, manifolds, etc?
My way can't be easier. Take out the T-stat, turn on the engine and suck 3 gallons of AF in and done.
And that's for a raw water cooled engine. Fresh water cooled? Same procedure except you don't even need to remove the T-stat.

I take it that what you're saying is you don't drain any of the water? If you're comfortable with doing it that way then so be it but you run the risk of diluting it well below its spec, especially with just 3 gallons of AF. I wouldn't recommend it in any case but certainly not up my way with the winter temps we get here or in NY where the OP is from but whatever floats your boat!

Source of the post So how long does it take you to drain the block, hoses, manifolds, etc?.....

It takes me as long as I need to do it so I don't have to worry about it

[buster53]

Yes, Canada is a whole different ball game than here in Virginia. If I was there, instead of 3 gallons of -50, I'd probably use 4 gallons of -100.
Also, all of my boats have been fresh water cooled, which makes a difference. The only raw water cooled boat I winterized was my son's bowrider with a Merc 5.7 Alpha drive. Took out the T-stat, put earmuffs on the outdrive with a short piece of hose and poured AF into the hose with the engine running. Piece of cake and no issues in the spring.

[amanphoto]

This is what I did this year...

Close sea cocks
Clean Sea Strainer / vacuum dry
Remove (5 each side) Blue engine drains - watch for O-Rings
Take a short piece of stiff wire and poke it around in the drain hole to free any rust or scale
V-Drive - remove the two small square headed drain plugs ( front and rear of the upper housing - Water Drain” on the housing
Remove the hose from the lower (rear) end of the transmission cooler. Inspect the cooler for any debris.
Remove front left thermostat hose - drain
Remove front left and right exhaust coolant lines
Port engine - Remove hot water heater hoses (two)
Port engine - Blow out heater hose with air compressor (on low)
Port engine - Attach short loop hose to engine where heater was ~ Port engine
Replace 5 Blue engine drains with O-Rings
Replace V-Drive Drains
Fill left thermostat hose (block) with antifreeze till it comes out thermostat housing - 4 Gallons
Port Engine - Pump Antifreeze through hot water heater hose - 2 Gallons
Fill left exhaust coolant lines - 1 Gallon
Fill right exhaust coolant lines - 1 Gallon

Reattach all coolant lines

Place funnel on Sea Strainer
Sea Strainer - Place a piece of hose in pickup side to the bottom of sea strainer so suck all liquid
Fill sea strainer with Antifreeze
Run Engine until Antifreeze in drained out - 1 Gallon

Put all engine parts together

Loosen serpentine belt for the winter

[amanphoto]

Next year...

I drain all the water our of the engine and v drive through the water drain holes and don't remove any of the hoses. Run the engine and suck antifreeze through the sea strainer....

Question is - Will it enter the block or be pumped overboard because the thermostat is closed?

[amanphoto]

Source of the post So how long does it take you to drain the block, hoses, manifolds, etc?

It takes a little bit if time. No long, but it can be hard to reach some of the plugs on the sides of the engines against the fuel tanks. Buster53 - remove all the plugs on both engines. While the one engine is draining your removing the plugs on the other engine.