Uneven exhaust water return

[805hd]

Hello all!

I recently purchased a new to me 1987 cobalt with a BBC and Alpha drive. The engine was pulled to replace a coupler. While it was out I did quite a few other things to it. Since then the engine has been reinstalled and runs great but I’m having a few issues..

Port side exhaust GUSHES water while starboard side barely returns anything. Lots of steam.

The impeller is in good shape, and the raw inlet that runs through the transom is wide open and clear. The thermostat housing seems to be in good shape currently running a 160f thermostat. With brand new manifolds, risers and elbows.

I pulled the hoses from from the manifold that feed water from the thermostat housing and ran the boat. Very poor return on the starboard side which makes sense since this is the same side as the exhaust with poor water return leading me to believe the restriction in somewhere from the thermostat housing back and not the manifolds risers or elbows. I just can’t seem to find it.

The boat running on the hose gets up to about 180f at the temp gauge and hovers there. Using a IR temp gun the port side elbow is 140f and the starboard side elbow is 150f.

I understand that I won’t get perfect 50/50 return out of the exhaust, especially off the hose but right now I’m getting about 90/10 and that just can’t be right.

Anyone have any ideas?
The only thing I have yet to check is the PS fluid cooler.

 

[achris]

...I understand that I won’t get perfect 50/50 return out of the exhaust, especially off the hose but right now I’m getting about 90/10 and that just can’t be right.....

It is. 'Path of least resistance'....Once you get on the water and there's a bit more water flowing, together with a bit of back pressure on the exhaust and cooling systems, then the flow will 'even out'....

Chris....

 

[JerryIrons]

My boat acts like that all the time on the hose. It used to freak me out as well, especially after I did work and thought, what did I eff up? As long as you aren't overheating, don't worry about it until you get on the water.

 

[cheswest]

I had this issue last year and discovered part of an exhaust shutter that must have separated from the previous owner and had gone down and jammed close to the bottom...they replaced the shutter but never recovered the piece. I got it out with a pick-up tool.

 

[805hd]

The boats through hull exhaust. I’m at the point where I just want to go dip it and see if it makes a difference but still, it never had this problem before and I’m starting to get pretty concerned as to why it’s having it now.

 

[Scott Danforth]

turn the boat/trailer around 180 and the other side will have the issue. short of making the engine perfectly level, one manifold will always be higher than the other.

 

[805hd]

this is the water return from the impeller at idle. Was imagining I would see more flow. Even at lower rpm?

 

[GA_Boater]

What is the water source in the pic - Hose, barrel or lake?

 

[805hd]

Hose...

 

[805hd]

I found this diagram online tonight, it depicts the opposite of how my cooling system is configured. This image shows the hoses from the thermostat cap running to the manifolds and the hoses off of the tee running to the elbows. Mine is opposite of that. Which is the correct configuration?

 

[QBhoy]

It is. 'Path of least resistance'....Once you get on the water and there's a bit more water flowing, together with a bit of back pressure on the exhaust and cooling systems, then the flow will 'even out'....

Chris....

This is your answer in a nut shell. My boat does the same. Corsa marine side exit exhausts. Just flows to where ever is easiest. If you have the captains call switchable like mine...it also flows out all exits available too. Not all out the sides. Even an inch lost on the trailer or water to either side shows a difference in flow.

 

[QBhoy]

Only slight afterthought that came to me there. The riser to manifold gaskets. Are they the right ones ? And right way on that side ?
If she is on a trailer...jack up the higher flowing side to lower the lesser flowing side and see what happens.

 

[GA_Boater]

Hose...

You cannot diagnose any water flow issue on a hose. A hose can't supply the needed volume and you could take the impeller out and see the same thing as post 7 with the motor running or not.

Is the hose routing diagram in #10 for your motor?

 

[vetplus40]

I don't want to "derail" the thread, but can someone briefly explain the double arrows depicted for the opening on the left side of the engine? This dual flow has me a bit confused.

 

[GA_Boater]

Lower is the circulating pump in and upper is out to the thermostat housing. A poor drawing if you aren't familiar with how it works.