starboard exhaust still running hot

[gmcleer]

John and company,

I have posted a few times about the starboard side of the engine running hotter than the port. I have played around with the hoses and hot water heater hoses to no avail. I finally picked up an IR gun from Sears. Here is what I found.

At hot idle after a run: Starboard 117F and Port 90F
After a run at 3400 RPMs: Starboard 173F and Port 110F

When I took these temps the hot water heater hoses were plugged to removed the hot water heater from the loop. The hot water heater draws from the starboard side of the t-stat housing and returns to the circulator pump. The t-stat housing at idle was around 130F.

The engine temp on the guage is 170F at idle and 175F when running. Oill pressure is good, it will drop after a hard run but return after a few minutes at lower RMP. Oil is also clean, no signs of water.

I'm thinking it could be a head gasket with a very slight leak or a blockage in the head or block or just less flow to that side of the engine. Exhaust manifolds, 6" extentions, risers, circulator pump and sea water impeller are all new.

I have heard that you can run acid through the system to break up any blockages, but, that sounds that an invitation for additional problems.

Any thoughts or should I just leave well enough alone?

Thanks,

 

[H2ONUT]

My issue was the port manifold, it was plugged solid with rust. You say yours are new.

Is it possible that the gaskets between the risers and elbows were installed wrong?

Did you do the work or have someone do it, I can't remember what you had posted before.

 

[gmcleer]

I had the work done by a mechanic. Who is MIA by the way?! I took apart the riser and extention, all was well. The new gaskets/install made no difference.

 

[H2ONUT]

Who is MIA by the way?!

:huh:

 

[PlayDate]

John and company,

I have posted a few times about the starboard side of the engine running hotter than the port. I have played around with the hoses and hot water heater hoses to no avail. I finally picked up an IR gun from Sears. Here is what I found.

At hot idle after a run: Starboard 117F and Port 90F
After a run at 3400 RPMs: Starboard 173F and Port 110F

When I took these temps the hot water heater hoses were plugged to removed the hot water heater from the loop. The hot water heater draws from the starboard side of the t-stat housing and returns to the circulator pump. The t-stat housing at idle was around 130F.

The engine temp on the guage is 170F at idle and 175F when running. Oill pressure is good, it will drop after a hard run but return after a few minutes at lower RMP. Oil is also clean, no signs of water.

I'm thinking it could be a head gasket with a very slight leak or a blockage in the head or block or just less flow to that side of the engine. Exhaust manifolds, 6" extentions, risers, circulator pump and sea water impeller are all new.

I have heard that you can run acid through the system to break up any blockages, but, that sounds that an invitation for additional problems.

Any thoughts or should I just leave well enough alone?

Thanks,

Hmmm... Let's start with the easy part...stay away from the acid! There are three steps that would really be helpful that don't require a mechanic to complete:


1) I gather from your discription that the water heater is disconnected from the engine. The correct way to bypass this is to simulate a loop as opposed to blocking off the hoses. Simply run a loop of hose between the tstat to the circulator pump.

2) Using your new IR investment, please give me IR readings on the manifolds, risers and elbows for each side. What I am looking for is temp differences between the components with the engine running and hot...including the tstat housing.

Make sure when you take the readings, that you do so on a non-glossy part of the component. Glossy surfaces can produce inconsistent readings. Such as a temp gauge reading 170 and the tstat housing reading 130. The sensor for the gauge is usually located on the tstat housing. The reading should not have a 40 degree difference to the gauge.



Optional -if you feel comfortable with the procedure.

3) If we still have a temp difference, we need to check if the problem is flow related. The way we do this is to swap the hoses that feed the elbows on each side. This way if the problem switches sides, we know we have a flow problem (we would do the same thing to check the manifolds) . All that is required is two lengths of hose and four hose clamps.


Don't worry about the head gasket at this point.

-John

 

[gmcleer]

John,

Should I pick up a few feet of hose and reverse the flow to the manifolds? What RMP do you want me to take the temp readings at? I will take readings of the mainfold, extention, riser and t-stat housing anywhere else?

Thanks

 

[PlayDate]

John,

Should I pick up a few feet of hose and reverse the flow to the manifolds? What RMP do you want me to take the temp readings at? I will take readings of the mainfold, extention, riser and t-stat housing anywhere else?

Thanks

Let's start with the readings you get and go from there. Warm the engine up so the engine temp gauge is around 165-170 degrees and take the readings at 1000 rpm. That will be our baseline.

Reading points:

Port
-exhaust manifold
-riser
-elbow

Starboard
-exhaust manifold
-riser
-elbow

Intake manifold
tstat housing
temp sensor

Was the water heater bypass correctly done? If you get a chance, please shoot a digital photo of the tstat housing. What I am looking for is whether they installed the cooling hoses correctly.



-John

 

[gmcleer]

John,

Sorry for the delay. Here are the temps taken at 170F on the guage and 1000 RPMS.


Reading points:

Port
-exhaust manifold - 90F
-riser - 91F
-elbow - 92F


Starboard
-exhaust manifold - 111F
-riser - 111F
-elbow - 110F

Intake manifold - 101
tstat housing - 140F
temp sensor - 145F

I'm not having much luck with the photos.

Thanks,

 

[PlayDate]

170F on the guage Odd, given the other readings

1000 RPMS Good

Port
-exhaust manifold - 90F Good
-riser - 91F Good
-elbow - 92F Good


Starboard
-exhaust manifold - 111F Good
-riser - 111F Good
-elbow - 110F Good

Intake manifold - 101 Good
tstat housing - 140F Good
temp sensor - 145F Good



Great job getting the readings. Port and Starboard look pretty good. Having a difference of 10 to 15 degrees is not that big of a deal as long as manifold/riser/elbow are similiar temperatures on their respective sides. BTW did you check to see if the water heater bypass was done correctly (looped hose)?

What strikes me as odd is the temp gauge being that far off. All temps are consistent with an engine operating at 145 to 150 degrees. Yet the gauge reads 25 degrees higher than the IR reading on the sensor. We will get back to this.

I would like you to try a procedure so that we can rule out your impeller. There is another thread "hot riser" that I would like you to take a look at. Basically with the engine at idle, pull the starboard hose at the tstat to check the flow at idle and at 2500 rpm. I just want to make sure we do this before you take the boat out and run it to get the engine hot for another set of readings.

-John

 

[gmcleer]

John,

I have observed the water flow at idle. After reading the suggested post. I will test the flow again at idle and at 2500 rmps. Can I check the flow where the water hose enters the bottom of the exhaust manifold? Also, can I run the boat at 2500 rpms at the dock? A bay test may be difficult.

Thanks,

 

[PlayDate]

John,

I have observed the water flow at idle. After reading the suggested post. I will test the flow again at idle and at 2500 rmps. Can I check the flow where the water hose enters the bottom of the exhaust manifold? Also, can I run the boat at 2500 rpms at the dock? A bay test may be difficult.

Thanks,

Just check it at the dock. You can check either the manifold hose or the elbow hose whichever is easier to get to. I would definitely do the starboard side. The engine does not have to be hot for this test.

Also, please confirm that the water heater was bypassed correctly with a loop of hose. If this is not the case, it will disrupt cooling flow to the starboard side.

Let me know,

John

 

[gmcleer]

John,

The hot water hoses are connected together forming a closed loop and were that way when I took the previous temperature measurements. I ran the boat at idle and brought her up to around 2600 rpms with the hose feeding the starboard manifold disconnected at the t-stat housing. As rmps were increased there was a slight increase in the flow rate of the water. There appears to be pleny of water flowing. Below are diagrams of the cooling system and exhaust. The water heater hose replaces plug 2 in the diagram of the t-stat housing and then returns the water thru a second hose to the circulator pump. I have 6" risers between the exhaust manifold and the elbow. The parts were all replaced in March and I took apart the starboard side exhaust (riser and elbow) about two or three weeks ago to ensure there was not a blockage or an incorrect gasket

I really appreciate you taking out the time to help me. Hopefully I will have an opportunity to return the favor.

Thanks!!

 

[PlayDate]

Excellent work!! The diagrams are very helpful especially the version of tstat housing you have.


What you have checked so far:

Warm engine test ----ok
Impeller test ----ok
port/manifold/riser/elbow flow ---ok
star/manifold/riser/elbow flow ---ok
tstat temp ---ok


The last test is a hot engine test where you run the boat at speed for 15 minutes and repeat your temp readings at the same locations you took the first set. It's best to have someone else with you so that you can stop (keep engine running) the boat and shoot all the readings in 30 seconds. The components will heat up quickly so start with the starboard side and then move to port. If it takes you longer than 30 seconds....the temp differences between the sides will be distorted.


Also take note of the temp gauge so that we can see if the gap between the gauge and the IR gun remains when the engine gets hot.


If we still have a material difference between the sides then we will move on to checking a few more things. Sometimes the casting of new manifolds have issues where internal passages are partially blocked making one side hotter than the other. It's not a big deal unless there is a material difference in heat. The easiest way to check it is to swap the manifolds/riser/elbows from starboard to port and recheck the readings. If the temperature moves with the manifold we have our answer. If it doesn't we start looking for a lean condition on the starboard side.

-John



-John

 

[gmcleer]

John,

Here are the latest readings. I ran the boat at 3400 rpms for about 20 minutes then took the readings below. Could a bad plug wire cause a lean condition heating up the starboard side? Should we pull some spark plugs? Also is the port side too cool??


Reading points:

1000 rpms -- 3400 rpms

Port
-exhaust manifold - 90F -- 100F
-riser - 91F -- 105F
-elbow - 92F -- 105F


Starboard
-exhaust manifold - 111F -- 173F
-riser - 111F -- 180F
-elbow - 110F -- 180F

Intake manifold - 101 -- 101F
tstat housing - 140F -- 150F
temp sensor - 145F -- 160F

Thanks!!!!

 

[PlayDate]

John,

Here are the latest readings. I ran the boat at 3400 rpms for about 20 minutes then took the readings below. Could a bad plug wire cause a lean condition heating up the starboard side? Should we pull some spark plugs? Also is the port side too cool??


Reading points:

1000 rpms -- 3400 rpms

Port
-exhaust manifold - 90F -- 100F
-riser - 91F -- 105F
-elbow - 92F -- 105F


Starboard
-exhaust manifold - 111F -- 173F
-riser - 111F -- 180F
-elbow - 110F -- 180F

Intake manifold - 101 -- 101F
tstat housing - 140F -- 150F
temp sensor - 145F -- 160F

Thanks!!!!

Nicely done (except where is my temp gauge reading?)

I think H20nut can answer this.....something is not right with the port side. While the starboard is a bit warmer than I like, the port side is way too cold. Unfortunately, the way I would determine this once and for all is to swap the components port to starboard and run the engine back up to speed.

If the problem switches sides we have our answer. To do this, you have to pull the plugs so we can check for a lean condition (which I doubt) at that point.

Is this something you will need a mechanic to complete? If it is, this then I will give you my phone number so that I can talk to him before he gets started.

It's not a difficult job but if you haven't done it before it can be. In the meantime, please check the water flow to the port side manifold.

The good news is that you are getting close. I know it is frustrating.

-John

 

[H2ONUT]

Very similiar to my problems... however I could get those readings right at the dock.

I am really curious to see what this turns out to be.

BTW, been running great. No issues... yet... :grin:

Depending on where you are in NY, I'd be willing to help you switch everything, it's not difficult at all. It's a real PITA to mount the manifolds by yourself...

 

[PlayDate]

Very similiar to my problems... however I could get those readings right at the dock.

I am really curious to see what this turns out to be.

BTW, been running great. No issues... yet... :grin:

Depending on where you are in NY, I'd be willing to help you switch everything, it's not difficult at all. It's a real PITA to mount the manifolds by yourself...

That's great news about your boat. I knew you could have diagnosed this after all you went through. Yeah, I'm thinking something still isn't right from a cooling perspective on gmcleer's boat. I doubt we have an internal problem with the motor. More likely a blockage.

-John

 

[gmcleer]

John,

The engine was running at around 175F or so the gauge is not that clear. Sorry I forgot that info. I keep wondering if the water heater flow is effecting the starboard side or could a blockage somewhere direct too much water to the port side? or is it ignition/fuel related?

I don't know when the spark plug wires were last changed. The mechanic said I shouldn't bother changing them, but now I am beginning to wonder.

I have already pulled off the riser and elbow before and diddn't have any trouble. I can pick up some studs to make changing the manifolds more managable, but I wonder if changing the wires, cap and rotor would be worth doing or am I kidding myself?

Thanks,

 

[H2ONUT]

I don't think it's ignition either. I'll bet you have a bad manifold casting.

 

[PlayDate]

I'm with H20Nut on this, let's stay away from the ignition at this point. The first thing I want you to check before we go any further is the water flow going to the port manifold at 1000 and 3000 rpm. The engine does not need to be hot for this test.

I want to take a moment and also address your concerns regarding the hot water heater. Most marine heaters get hot one of two ways: 1) electric heat 2) engine heat. In your case, the engine heat has been disconnected from the water heater. If you were to cut open the water heater you would effectively see a loop thru the unit for the raw water from the engine to flow. On your first post you indicated that these hoses that come from the engine had been "plugged" which would create a flow disruption. Now you know why I kept asking if a loop of hose had been used instead of plugs. A loop of hose will perform the same function as having it properly connected to the water heater. The water heater itself does not remove a material amount of heat from the water so a loop of hose will be as effective. It is also ok to plug the tstat housing and water pump directly. What is not ok is to plug the hoses.

As to swapping the manifolds yourself: The manifolds each weigh 60 lbs on a 7.4. To switch sides you have to disassemble the risers and elbows which weigh another 30 lbs. Since you have already taken the risers apart we can try to do this over email. I just want to make sure you are up for it. A qualified mechanic can get it done for you in two hours. So, is it worth 6-8 hours of your time?

After you remove each manifold, put a water hose to the manifold fitting to make sure water runs through it properly. Providing the flow to the port manifold is ok, I'm hoping we have a internal blockage in one of the manifolds which is creating the problem.


It's up to you.

-John