350Q water flow in riser

"I try to figure out if a 350Q

"I try to figure out if a 350Q riser has a leak or blockage.
Concrete questions:
- Where does the main water exhaust meet the gasses? I presume somewhere after half way through riser? Or is it separated all the way and comes out the small oval hole above the main exhaust on the rear of the riser?
- Where does the secondary water meet the gasses? In the riser? Or is this directly connected to the oval hole mentioned?
- What is the usual first point of failure of this riser? When I blow on the main water entrance there is no back pressure. Air is coming out of the main exhaust (as I expected), but also out of the secondary water entrance on the top left side (as I did not expect).

Thanks in advance for the help.

Andre Huizing"

"If you have some photographs

"If you have some photographs it sure would help narrow things down.

On a raw water cooled "Q" with log exhaust manifolds there will be a hose on each riser that connects to a housing on the engine block just forward of the transmission. At the risers there will be pressure relief valves that inhibits water flow out of your engines until a certain water pressure is reached. Then the pressure relief valves open and a whoosh of water exits out through the exhaust. Other than that, the exhaust manifolds have a water jacket hose connection on each forward end cap that allows a constant cooling water flow. A non-contact thermometer may alert you to hot spots that are not receiving the proper cooling.

I hope this has helped. It really only applies to one of many possible configurations."

The first question is do you h

The first question is do you have a closed cooling system or a raw water cooling system cause it changes everything.

"It is a raw water, very stand

"It is a raw water, very standards setup, cooling system. With the relief valves etc.
I don't have problems with the exhaust manifold, only the starboard riser.
My investigations have progressed in the mean time. I know now that NO water should be mixed with exhaust gasses in the riser. It should all flow out the hole on the rear of the riser above the exhaust opening.
I filled the riser via the normal entrance of water on the front. All water came intially out of the small hole. However after a while I saw water slowly appearing in the exhaust, indicating a leak. After hammering with a screwdriver in the main exhaust hole I broke through the iron (or what's left of it) and the water came pooring through the hole into the exhaust.
Hence this was probably my problem as exhaust gasess (being under higher pressure than the water) have entered the cooling jacket.
I'm still not sure on how exactly the cooling jacket is formed in the riser?
Because the hole is fairly good reachable I will try to repair it by cutting away the corroded iron and using something like JB Weld.
I would love to use a new riser, but that is only available in the states and will cost me about $400 in shipping alone.
I would appreciate any remarks on the above.

Thanks,
Andre"

"Sorry, I have no clue other t

"Sorry, I have no clue other than to remove everything, clean and repair if possible. Just removing them is a test of patience in itself.

The best of luck."

"On the "art of removing&#

"On the "art of removing": all bolts came off quite easily, except for 1. On the starboard riser the lower right bolt is a socket screw (I think that's the English word, I mean a screw that is turned by a hex socket).
It is 5/16" and it won't move. I have now unbolted the entire exhaust manifold including the riser.
Any tips/tricks on removing this 1 bolt?"