Water Circulation Problem - 5.7 raw water cooled

[zealer]

Hi all,
Recently I dropped a new 5.7 vortec long block in my boat. Was out the other day doing some testing and tuning and the starboard riser got so hot that it ballooned and melted the exhaust coupler on the y-pipe (also the flapper is gone- I presume it has melted/fallen down). Water was spraying out where the rubber tube melted/ripped apart so some water is indeed getting through the riser but I don't know if it is sufficient volume. Engine temperature was normal throughout at 140-150.

Regarding the risers, the water is circulated through the slotted passages (if looking at a gasket, for reference) that are outside the main center passageway, correct? I have the hoses routed as per this diagram: http://www.marineengine.com/parts/mercury_marine_parts/sn/0K002501/457L100KS/1939_140

I've attached a picture of my engine showing the way I have the hoses set up at the thermostat housing (which I'm pretty sure is correct - or at least it matches the diagram above).

I'd like to use compressed air to see if I can check the 'flow' of the risers. When I assembled the engine I did blow air through the manifolds and I thought I was getting good circulation. I also did this with the thermostat assembly.

Just looking for some advice and general information as to how the water system circulates so I can troubleshoot it and fix it effectively but not waste money on unnecessary parts.

For the record, serial number is 0K002501 (heads upgraded to vortec) and it is raw water cooled.

 

[NHGuy]

I'd check inside the starboard side of the exhaust y pipe for chunks of flapper.
See if you can send air or water through the starboard riser via the exhaust manifold cooling water inlet.
Also check the cooling water discharge hoses for flow. You can start the engine for a short moment to see how much water comes to each side. If the starboard side is still flowing poorly look to the cooling water distribution system in the thermostat housing.

 

[zealer]

OK thanks will do. Just to confirm I understand the proper circulation - the first inlet on the right side of the thermostat housing (looking at the engine) is the main inlet. The water is circulated through #2 and #3 (see diagram) to each respective manifold and is pumped up through the riser jacket and out into the y-pipe. The thermostat does not affect these manifold hoses as all water is eventually discharged through the manifold and then overboard, correct?

 

[alldodge]

Since you have riser extensions, I think one of your gaskets are wrong, or in wrong order. Do check both sides to make sure they are both set up as in the pic

 

[scoflaw]

New water pumps, and exhaust on your new engine ?

 

[rickasbury]

All Dodge is the man....listen to what he is saying!

 

[zealer]

Thanks for the help everybody and particularly to AllDodge. Disassembled it all and found a blockage (acorn) in the cooling hose. Replaced flapper and coupler tube. Runs cool and great circulation.

On another note, the lower shift cable now needs to be replaced. One thing fixed and another to go... funny how these things time themself...

 

[alldodge]

An acorn, dang wonder how that got in there, kind a squirrely if ya know what I mean

 

[zealer]

Yeah when I was assembling the engine for installation I did find acorn shells and I thought I blew everything out nice and proper. Clearly not the case! Now I understand a little better as to why my dog hates those furry creatures with such passion.

Looking for new lower shift cable (probably melted on the hot exhaust) and am struggling to find the correct part number. There are many options form Sierra (different lengths) but the only Mercury/Quicksilver number I can find is 865436A03. Can anyone confirm if this is correct?

Its an alpha one gen 2 drive serial 0k041160

 

[alldodge]

Part number 865436A03 is the correct part (item 10)

https://www.mercruiserparts.com/bam/subassembly/30860/1942/50