Mercruiser 4.3 MPI Q's

[Bondo]

What it takes to keep those block drains clear is a set of picks with different angles that enables you to dig out rust & sand that accumulates in the cooling passages at the bottom of the block. This is why I feel all cast iron inboards should be closed cooled: because of how cast iron corrodes…it flakes off more or less chronically and will never stop, so those drains are destined to clog sooner or later.

Ayuh,...... For that reason, right there, is why there's a 4" ssteel deck screw that lives on my intake manifold,.....
Pull a drain plug, poke it with the screw, 'n the water, 'n crud gushes into the bilge,......

 

[Lou C]

Yep, for some reason (I think it is because of the large size of the old Delco starters) mine has a right angle fitting on the side with the starter, this one I really had to dig at to get it to flow one year, since then it has been fine. I would like to change it but I don't think fooling with those fittings on an engine as old as mine is a good idea...lol.....

 

[DcMb]

Thanks for the responses. Appreciate it!

Just try to idiot proof this with images. In the pic:

https://imgur.com/a/bcW5kv0

I'm ASSuming that:

1. Is water coming into the engine from the pump
2. is water entering the stat housing
3. is the stat housing
4. cold water supply to the right
5. cold water supply to the left

The down hose by 1 is to the single point of failure drain and should be the lowest point in the system?

So pull 4 and 5 and flush both with coolant with the drains open.

Pull 2 and flush backwards with coolant?