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New Manifolds, one has low flow

F

freebeerisgood

Member
Engine: 1999 7.4MPI Fresh water cooled / ~750hrs

Today I replaced the manifolds and 3 Inch risers on my engine, re using the elbows as they are in good shape from what I can tell. I also replaced all the Coolant hoses(only those is the closed loop system), plugs, wires, rotor ect...

Ran the engine after and the Port side has almost zero water flow out the exhaust. The Startboard side has basically ALL the raw water flow coming out. very odd, I have never seen anything like it, even when the manifolds stop flowing very well when they age, its never this bad.
I shut it down after just a minute or two, and pulled the raw water hose off the Port manifold and it was almost like it was pressurized, likely building up pressure from whatever is obstructing flow, at least that makes sense to me. Flow was always equal prior to replacing the manifolds. Water pump is almost new, andI ran it before I changed manifolds, all checked good.

What can cause this?
I can't even think of way to flip the gaskets to obstruct flow, looking at the olds ones.

The pressure built up on the manifold makes me wonder, I'll likely take them apart tomorrow.

Thanks any suggestions
 
next to imposable to plug them using the correct gaskets. If this is the first run of the season could a critter have crawled up the exaust?
Are these standard or dry joint manifolds, have to ask even though the "4 slot" gives me the answer
 
Did you rod out the fitting going into the manifold sounds like it may be plugged or severly restricted. Pull the fitting off and see if air pressure flows free through the manifold and elbow?
 
Bt Doctur said:
next to imposable to plug them using the correct gaskets. If this is the first run of the season could a critter have crawled up the exaust?
Are these standard or dry joint manifolds, have to ask even though the "4 slot" gives me the answer
Click to expand...

Standard. The 4 slot gaskets came off with the old. Same style installed with the new.

I put them on this morning, they had been apart for a few weeks awaiting parts. The only place anything could have made a nest was downstream the butterfly valves in the Y pipe as nothing else was installed on the boat for a few weeks. I'd call it highly unlikely.
 
kimcrwbr1 said:
Did you rod out the fitting going into the manifold sounds like it may be plugged or severly restricted. Pull the fitting off and see if air pressure flows free through the manifold and elbow?
Click to expand...

The raw water fitting on the bottom of the manifold? I'm not sure what would be in there, they are new. I installed the fitting today prior to mounting the manifolds.
 
Where the water and exhaust finally meet are a series of slots and holes that can plug up. I had to rod these holes out with a power drill and coat hanger wire.

Jeff
 
fastjeff said:
Where the water and exhaust finally meet are a series of slots and holes that can plug up. I had to rod these holes out with a power drill and coat hanger wire.

Jeff
Click to expand...

Inside the stainless elbows? As I understand it thats where the water and exhaust finally meet, they were not replaced. Maybe I'll pull the port one and check it out, its the only thing I can imagine having blockage as the manifolds and risers are new.
 
UPDATE:

I hooked a hose to the raw water pump outlet with a hose clamp, unhooked the outlets where they attach to the manifolds, only the STARBOARD has flow, PORT is a dribble, just like when running. Before that I backlashed the system to ensure no impeller parts were in there, nothing.

To me this seems to be an issue internal to the heat exchanger.
Are there decent options to clean the heat exchanger? Im thinking wire brushes up and down the tubes for a start, maybe an acidic solution?
Any experience with this?
 
Heat Exchanger??????? Both port and Sbd elbows are fed from a common set of tubes. On some heat exchangers, there is a raw water dump to the elbows that has a built in, i.e. part of the HE "Y". Perhaps one of these is plugged, but the tubes... no.


Re: "replaced all the Coolant hoses(only those is the closed loop system)"... Did you replace the hoses from the HE to the elbows?
 
Did you hook the water hose directly to the manifold that has low flow? Maybe the high house pressure will clear the blockage? All you need to do is follow the flow path are you getting good flow from the two hoses going into the manifolds? Did you remove and rod out all the ports good in the thermostat housing? Are all the hoses new? If you have good flow to the manifolds you should have good flow out as well. Your making it way more difficult that it needs to be IMO.
 
Pay attention guys, hoses were removed from the manifolds raw water into the HX comes out to a T or Y fitting to direct the water into the manifolds.
If the HX has seprerate outlets for the manifolds then the HX has a clog. If a common outlet going to a T or Y fitting ,then might be a hose plugged, clogged?
Wondering if the replaced hoses went to the wrong connections?
 
Bt Doctur said:
Pay attention guys, hoses were removed from the manifolds raw water into the HX comes out to a T or Y fitting to direct the water into the manifolds.
If the HX has seprerate outlets for the manifolds then the HX has a clog. If a common outlet going to a T or Y fitting ,then might be a hose plugged, clogged?
Wondering if the replaced hoses went to the wrong connections?
Click to expand...

and pulled the raw water hose off the Port manifold and it was almost like it was pressurized,



The exchanger is clear. The exhaust is restricted.
 
kimcrwbr1 said:
Did you hook the water hose directly to the manifold that has low flow? Maybe the high house pressure will clear the blockage?
Click to expand...

I did do that just about an hour ago, it has flow. I also pulled the elbows and re inspected, no blockage at all.

kimcrwbr1 said:
All you need to do is follow the flow path are you getting good flow from the two hoses going into the manifolds? Did you remove and rod out all the ports good in the thermostat housing? Are all the hoses new? If you have good flow to the manifolds you should have good flow out as well. Your making it way more difficult that it needs to be IMO.
Click to expand...

I mentioned that I have low flow out of one of the hoses that enter the manifolds, hence my reason for believing its in the exchanger. Thermostat isn't in play here, its freshwater cooled. I don't think I'm anything too difficult, how do you mean?
 
Bt Doctur said:
Pay attention guys, hoses were removed from the manifolds raw water into the HX comes out to a T or Y fitting to direct the water into the manifolds.
If the HX has seprerate outlets for the manifolds then the HX has a clog. If a common outlet going to a T or Y fitting ,then might be a hose plugged, clogged?
Wondering if the replaced hoses went to the wrong connections?
Click to expand...

It has two outlets, one per manifold and a single inlet. The only hoses that were replaced were hoses that carry coolant, no saltwater hoses were as of yet. Hoses are hooked correctly for sure.

Since the UPDATE I posted I have pulled the heat exchanger, and found some of the tubes to be flogged, specially the ones near the outlet for the PORT manifold. I used a pipe cleaner on all the tubes, filled the exchanger with muriatic acid/water (probably 15% Muratic) and ran a pipe cleaner in the tubes again. Repeated the soak once more and now I can see through all the tubes, squeaky clean.
 
Docksidemarineservices said:
Chances are this is your problem. How old are the elbows? Probably clogged. Why wouldn't you replace everything? The elbows are the failure point.
Click to expand...

Docksidemarineservices said:
and pulled the raw water hose off the Port manifold and it was almost like it was pressurized,

The exchanger is clear. The exhaust is restricted.
Click to expand...

Initially this was my thought. I hooked a hose to the manifold fitting where the raw water enters and it had flow, then I proceeded to verify the exchanger has low flow on the port side with a garden hose hooked to the water pump outlet, and the hoses on the manifolds removed.

I have cleaned the exchanger with a deluded muriatic acid mix and a pipe brush. The tubes were terribly clogged. I'll have it back together hopefully tomorrow for a run to see how it helped, I imagine it will be night and day.
 
UPDATE:
I finally got around to putting the HX back on the engine. While the HX tubes were pretty gross, and now look squeaky clean, I have the same problem.

I'm unsure how to proceed. I didn't one more water flow test with the hose as follows
- Attached a garden hose to the outlet of the raw water pump (with hose clamp, holds pressure)
- Unhooked both outlets of the heat exchanger where they enter the P and S manifolds
- Turned on full water pressure.

Result: I still have low flow on the Port side. This time, I used my hand to plug the Starboard side, and the water flow shifted to the Port side, so its not actually "plugged", it will flow water, but when the Starboard is open it seems like it takes the path of least resistance.....

To me, it seems there is something going on internal to the HX? How often do they malfunction internally? I can see through every single tube when I remove the end caps, but I'm not intimately familiar with the inner workings, so I'm unsure how to tell if something is wrong with the HX aside from inspection the tubes with the end caps off.
 
Screen Shot 2017-04-15 at 4.39.08 PM.jpg
To give you a visual of what I mean by low flow comparing the two, the Left is the Starboard side, the Right is the Port.
 
Is your engine running any warmer than usual? Have you traced water temps with an infrared temp. gun on both heads,risers ETC.
 
johnnygjr said:
Is your engine running any warmer than usual? Have you traced water temps with an infrared temp. gun on both heads,risers ETC.
Click to expand...

As you can imagine the Port manifold is getting very hot with just the dribble of water passing through it and the Starboard is staying cool, but thats expected with this water flow issue I'm having. I'm not running the engine long enough to get up to temp while the Port manifold is getting such low flow, the engine has never ran hot in the past.
 
One of my engines did that when some crud blocked the opening in the T-stat housing for the starboard manifold. I found it by removing the hose (which had low flow). The only thing left was the T-stat housing itself.

Jeff
 
fastjeff said:
One of my engines did that when some crud blocked the opening in the T-stat housing for the starboard manifold. I found it by removing the hose (which had low flow). The only thing left was the T-stat housing itself.

Jeff
Click to expand...

The engine is freshwater cooled, so no raw water through thermostat. I have the issue isolated to the Heat Exchanger I believe
 
I'm confused. In a MC 454 full closed ("fresh water") system, there should NOT be any raw water in the manifold. It is supposed to be part of the "coolant" system along with the block and a block-off plate should be gasketed between the manifold and the riser. Do you have a half-system in which only the block has coolant and the exhaust manifold, riser and elbow are raw water cooled?

In my full system, the raw water first comes from the through hull through the oil and transmission coolers before the raw water pump, then into the H/E in a single hose before exiting in two hoses to the risers and then up to the elbows. Cleaning the tubes in the H/E is a good step to restoring any raw water flow issues. Any impeller pieces should have been discovered when you open the end caps of the H/E.

If you suspect the problem is with the H/E, plug the intake from the raw water pump, disconnect the hose on the starboard side and put in a bucket. Insert a city water hose into the port side hose. If there is a blockage in the heat exchanger, the water flow into the bucket will be minimal and the back pressure should blow the city water hose out of the port hose. IF not, put the intake hose in the bucket and plug the starboard hose. If the same thing happens, you do in fact have an internal problem and the H/E and need to replace it.
 
freebeerisgood said:
Riser gaskets?

All 4 that came with the risers where the same. 4 large slots, one on each side
Click to expand...


The gaskets are incorrect.

Between the manifold and the 3" riser you should have the gasket with 4 large holes. Part Number 860232


Between the Riser and the elbow you should have a restrictor gasket with 2 large holes...Part number 860233
 
freebeerisgood said:
The engine is freshwater cooled, so no raw water through thermostat. I have the issue isolated to the Heat Exchanger I believe
Click to expand...
Just to be clear, you have a half closed cooling system, not a freshwater cooled system. It's called a half system cz the exhaust manifolds are not included in the part of the cooling circuit that has antifreeze. The manifolds are cooled by seawater (we say seawater even if it's on a freshwater lake). The engine is cooled by coolant mixture, just like a car. The "radiator" is the heat exchanger. You knew all that.
Next time you want to descale your heat exchanger just buy a couple gallons of white vinegar and fill/empty it a few times. The muriatic acid is too aggressive. We don't want you to dezincify the heat exchanger...they are awfully expensive to replace. The vinegar will go after the hard deposits without attacking the metal. Muriatic acid is super aggressive on zinc. Just drop a galvanized nail in muriatic acid, you'll see.
 
re: vinegar and salt deposits... I had a t'stat from an outboard that was a mass of crud. Overnight in a cup of white vinegar and it looked looked like new.... Also was able to see that it was the wrong t'stat (165) for use in seawater, and hence the accumulation of deposits. Your HE should not accumulate crud if there is sufficient raw water flow, i.e., never gets above 140 ish on the raw water side of the HE. Once temp of seawater gets much above 140 ish, the salts and other minerals start to precipitate out.
 
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