5.7 mercruiser raw water cooling system cleaning???

[peanutbay1]

I have removed the thermostat housing on my 5.7 mercruiser only to find the housing is shot and directly below the tstat in the intake manifold it had a black crud. This crud did not seam to be in the passages leading away from the tstat hole but I am sure they have some residual mung. Does any one have a reccomendation about cleaning the engine coolant passages with any cleaner with hot water????

 

[peanutbay1]

Re: 5.7 mercruiser raw water cooling system cleaning???

Any ideas?????

 

[PiratePast40]

Re: 5.7 mercruiser raw water cooling system cleaning???

Raw water systems should be relatively self flushing. Is it possible that the "black crud" is melted pieces of the raw water pump impeller?

 

[havasuboatman]

Re: 5.7 mercruiser raw water cooling system cleaning???

You can try to flush the system backwards thru the hoses that feed your exhaust manifolds.
But the Pirate is right, you need to figure out what that stuff is, because it is likely parts of your raw water impeller, either currant or a previous one.

 

[peanutbay1]

Re: 5.7 mercruiser raw water cooling system cleaning???

Its not impeller rubber as I removed the original which was fine and replaced it with new just 3 weeks ago. This was a bay boat and a person I work with that is a coast quard on the bay said it is sea mud from running shallow bay channels and it builds up at the tstat housing area. I was just curious if anyone ever used something like "mean grean" or anything to clean out their engine block coolant passages.

 

[jtybt]

Re: 5.7 mercruiser raw water cooling system cleaning???

You can do it the way you flush out regular auto blocks. Remove the hoses and knock out the 'freeze plugs'. Sometimes you find rocks in there from the casting