Draining Mercruiser 5.7

[alldodge]

This one gets debated every year quite a bit and as all things here at iboats it comes down to IMO two points.

Air doesn't freeze, so if you get all the water out the motor will be fine.

Some say filling with antifreeze after all the water has been removed will keep some rust down.

The way you did it is the way I have been doing it for years, just remember to poke something (long screw, small screw drive, wire) up in the hole so if it has a piece of crud there it will break free

 

[robinsbd]

I cut up an old wire coat hanger last year and poked into all the drains, and yes some crud came out and the water flowed faster after that.

When I removed the thermostat housing to circ pump hose, very little water came out of the thermostat housing and very little came out of the pump.

I have actually heard of problems caused by using antifreeze such as cracked blocks. Do you know why this would happen when someone used antifreeze?

 

[Bondo]

I have actually heard of problems caused by using antifreeze such as cracked blocks. Do you know why this would happen when someone used antifreeze?

Ayuh,.... Because they don't drain the block, before tryin' to put antifreeze in it,....

 

[NHGuy]

And anti freeze diluted with water freezes at some point. Sure, it's lower than 32 but the water raises the freeze temp depending on it's concentration percent.

 

[bruceb58]

I have actually heard of problems caused by using antifreeze such as cracked blocks. Do you know why this would happen when someone used antifreeze?

Because they try to put antifreeze in through the muffs and running the engine.

 

[robinsbd]

Thanks for all the great info.

 

[robinsbd]

Do you know if there are any cut-away pictures or diagrams of what the water passages actually look like in a typical mercruiser 5.7? I am just curious. I looked around, but I didn't find any. Perhaps that is proprietary info.

Thanks!

 

[thumpar]

The antifreeze will freeze before air will.

 

[alldodge]

Do you know if there are any cut-away pictures or diagrams of what the water passages actually look like in a typical mercruiser 5.7? I am just curious. I looked around, but I didn't find any. Perhaps that is proprietary info.

Thanks!

Never seen any. but they a pretty much an inner and outer walls open for water flow

 

[robinsbd]

Do you know of any trouble spots where there might be trapped pockets of water?

In general, my thought is that all the water would simply drain out because of gravity.

 

[Bondo]

Do you know of any trouble spots where there might be trapped pockets of water?

In general, my thought is that all the water would simply drain out because of gravity.

Ayuh,.... Go back to the top, 'n reread this thread,..... It's pretty much covered drainin' yer motor, a couple times over,.....

The trouble spots are the drains, ya gotta poke the crud outa 'em with the implement of yer choice,....

Pullin' the big hose off the circulatin' water pump drains the pump, another trouble spot,...

Yes, gravity is in play, water flows downhill, ya just gotta bust the dams of crud in the drain openin's,...

 

[robinsbd]

Thanks Bondo. I don't mean to keep beatin a dead horse. I guess I was just wondering if there were any trouble spots around the block besides the drains. I am very fascinated by the whole thing from a technical perspective.