Closed System Coolant Drain? Mercruiser 5.7

[RAW BAR]

I haven't been able to find where to drain the coolant out for a drain and fresh refill. Lots of info out there on the seawater side, but not much on the closed coolant side. Mercruiser 5.7 MAG Horizon I boards.

 

[Bill Curtis]

1. Drain the manifolds from the bottom by pulling off the hoses
2. Drain the engine block via the 1/4" plug on each side of the engine block
3. Drain the heat exchanger. Pull off hose?
4. Pull off big hose from the water pump.

 

[paulswagelock]

On my 496 I just had to pull the block drain on each side and nearly all drained out. I refilled with the same dexcool so I was not worried about any residual coolant remaining.

 

[RAW BAR]

1. Drain the manifolds from the bottom by pulling off the hoses
2. Drain the engine block via the 1/4" plug on each side of the engine block
3. Drain the heat exchanger. Pull off hose?
4. Pull off big hose from the water pump.

Any idea how to locate the engine block plugs?

 

[techmitch]

Any idea how to locate the engine block plugs?

They are usually just above the oil pan on the side's of the block.

 

[Espos4]

Any idea how to locate the engine block plugs?

They may not be easy to access in a twin engine 290.

 

[RAW BAR]

Might this be it? There's a similar one on the other side if the engine.

 

[RAW BAR]

They may not be easy to access in a twin engine 290.

After figuring out how to contort to change out my shaft seals last year (under the engine as they are v-drives) I feel like I can access anything on these engines!

 

[Bill Curtis]

Might this be it? There's a similar one on the other side if the engine.
View attachment 160644

That's the one of 2

 

[RAW BAR]

That's the one of 2

Thank you!

 

[Bruceflinch]

After figuring out how to contort to change out my shaft seals last year (under the engine as they are v-drives) I feel like I can access anything on these engines!

I feel like that is a job for a flexible little person!

 

[RAW BAR]

Related question, do the plugs need teflon tape or sealant before they go back in?

 

[Bruceflinch]

Related question, do the plugs need teflon tape or sealant before they go back in?

I would use either.

 

[Bill Curtis]

Since it's closed cooling and doesn't need to be removed often for draining, I use Aviators Permatex on them.

 

[Lazy Daze]

Related question, do the plugs need teflon tape or sealant before they go back in?

They should be bronze (or at least high quality brass) plugs (check yours - the color in your pic makes them look like they might not be). They don't need anything on the threads. It's OK if you want to use something - but bronze seals perfectly well without it. Just make sure to use something without metals in it.

 

[Bruceflinch]

They may not be easy to access in a twin engine 290.

Not easy on a twin 340’s either.
I cheated. Opened the plugs and they were plugged.
removed the thermostat And used a shop Vac. Pulled 26 liters of 27, in one. 25 in the other.