1989 268Da 7.4 bravo1 raw water cooled engine flush

[Handsome Transom]

I am doing maintenance for my cooling system I have done my pump as well as exhaust tubes and butterfly valves at the y pipe . I am changing all the hoses when they get here tomorrow I noticed they were all original and showing signs of approaching failure. I know no kidding original hoses on a 30 year old boat. I want to flush rust scale and debris from the cooling system since I notice a lot of scale in the hoses i removed as well as rust and deterioration of the nipples on the t stat housing. Can anyone reccomend products and methods to flush my block and clean the buildups that are no doubt inhibiting water flow in my block and other cooling system components. I want to do this in slip.
Thanks in advance Dave

 

[89PNWPC]

Did you get it all flushed? The reason I am asking as I am about ready to do a hose change out as well on my 2 454s and ran across your post.

 

[Handsome Transom]

Yes I flushed my engine after changing all the hoses with vinegar 2 gallons and 2 litres of coke classic after draining the block.and manifolds . I disconnected my water heater since it is new. . I filled the manifolds through the supply hoses and the block through the thermostat housing . Half gallon vinegar the double strength cleaning type in each manifold and a gallon in the block. Then added half if the coke split between the manifolds ant the other half to the block. Topped up to full with water . That was maybe a gallon total. I let the solution soak for 4 hours then reassembled and fired it up . Nice plume of rusty scale crud cane out the exhaust and although I was not overheating before my riser temps are even now where as prior my portside one was hotter than the starboard side . I am running about 145 normally and if running hard 148

 

[Handsome Transom]

Also notice the hose port side from the t stat housing that appears to be smaller than it's starboard brother . It goes to the manifold . I used 1 inch heater hose to replace it and ran a longer piece to be able to get a nice gentle curve in it rather than the 90 degree bends in the oem hose I attached a pipe securement to the bulkhead to run the hose through and keep it from getting caught up in the belts . I think this made the most difference for me since the hose has no restriction spots and is a slightly larger diameter than the original

 

[Handsome Transom]

 

[89PNWPC]

Also notice the hose port side from the t stat housing that appears to be smaller than it's starboard brother . It goes to the manifold . I used 1 inch heater hose to replace it and ran a longer piece to be able to get a nice gentle curve in it rather than the 90 degree bends in the oem hose I attached a pipe securement to the bulkhead to run the hose through and keep it from getting caught up in the belts . I think this made the most difference for me since the hose has no restriction spots and is a slightly larger diameter than the original

Thank you for sharing your trials and tribulations!!