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Overheating after elbow and riser replacement

Ngeogh

Member
I would appreciate some input on this one as I am about to be driven crazy trying to figure out what the problem is.

I recently undertook routine replacement of the elbows and risers on my 1986 Tiara 3100 and as usual removing the old risers was a nightmare but eventually they came off but as I was removing the very last stud that connects the riser to the exhaust manifold it broke off. I tried drilling it out to no avail, so this led to replacement of the starboard exhaust manifold. Then I foolishely thought that it might be a good idea to have the heat exchanger checked and cleaned, only to have the repair shop tell me it was no longer serviceable. So I now had to purchase a new heat exchanger.($1200)

Upon reassembly with a new exhaust manifold, new elbows and risers, new heat exchager and new cooling hoses, I start the motor and find that the raw water pump is frozen, so I replace the impeller and all seems well until our first sea trial and the motor is now running about 20 degrees hotter than usual. I checked the raw water flow at the risers and it seems normal, bled out the fresh water system at the the thermostat and did the typical checks for air pockets etc but all seems normal, no leaks and no coolant loss. However all parts of the motor feel hotter than usual including the new heat exchanger. I am begining to wonder if there might be a problem with the new heat exchanger or possibly a thermostat issue but before I start randomely replacing parts I would appreciate fresh input.

Any idea as to what might be going on here?
Thanks in advance
Ned
 
First of all, do yourself a huge favor and buy an infrared temp gun (no boater should be without one) to see what the actual temps are. You might be the victim of a bad temp reading.

But if she IS overheating. look for an air leak before the raw water pump. A tiny amount of air tends to murder the cooling effect.

Jeff
 
2X on Jeff's thoughts...

If they are the original "log style" exhausts, did you check to make sure the gaskets were installed correctly?

Finally, you are likely to have to purge the closed side after replacing all that hardware...
 
Thanks Jeff and Mark. I will check the temps and possible air leak this weekend. I assume the manifold should read around 160, what about the elbows and risers? There is a raw water filter prior to the pump which looks like it is original to the boat, and potentially could be the source of an air leak. Other than a visual inspection is there any other test you would recommend?

Not sure if they are the "log type exhausts" the elbows and riser are crusader #97772, four inch high riser with 3 inch outlet elbow "end style".
There are two gaskets and a block off plate between the riser and manifold with a single gasket between the riser and elbow. I am not sure how to check for incorrect installation without taking them apart again, which as you can imagine I would rather not do. Considering that there is a block off plate at the manifold I would think that an incorrect gasket installation would have to be between the riser and elbow. Is that correct? Is there any check other than disassembling the hardware for that?

To purge the fresh water side I added coolant until it appeared at the bleed screw on top of the thermostat housing and then ran the motor at 2000 rpm while adding coolant as needed per the instruction the the Crusader manual. Is there anything else I can try?
Thanks again for your advice.
Ned
 
That looks like the original log style parts...should be about 160 going into the exhaust manifolds - going out, should be hotter but not much.

The raw water going into the riser/elbow (depending upon how they are plumbed) shouldn't be more than 130 - and that will vary based on the outside the boat water temp...

What you are calling a filter is usually termed a strainer. It should have a basket inside and that needs to be clean...most have an access plate on top and they are a typical air leak spot...if they have gaskets, it wouldn't hurt to renew them.

The gaskets....here's the trick...if you look around their perimeter, you'll see little bumps - one or two, depending upon the gasket configuration...those tabs need to be "up" - either @ 12 o'clock, or at 10:30 and 1:30. The parts diagram will show you which one goes where...the exception is that either will work on the "raw water" side of the block off plate.

On the purge - sounds like you got most of it...depending upon where your heat exchanger is in the mounting slots, you may need to warm the engine a few times to liberate any trapped air...when the cold level in the heat exchanger stays consistent, the air is gone (and there are no leaks)...most engines from that vintage don't have the degas bottle so checking the heat exchanger is the only option.
 
You said that the raw water pump was frozen, did you do a complete or major rebuild or did you just replace the impeller? I was having temp problems and at the advise of a co worker I pulled the pump and did the major rebuild. That made a huge difference in my cooling. And Jeff is right about the ir gun.
 
I just replaced the impeller as the rest of the pump appreared to be in good condition. No play or noise from the bearings, etc. I think the impeller just froze from sitting to long while I was working on the rest of the motor. It pumps the same amount of water as the port motor so I think the pump is ok but I am going to check for air leaks at the strainer as Jeff suggested. I think that I might see if I can find a rebuild kit for the strainer.
Thanks
Ned
 
Question:
Were these the correct manifold to riser to elbow gaskets. IOW, once the new gaskets were in place, were all of the transfer ports open and free?
If there is a restriction at this area (for example... not all ports in gaskets open), seawater flow to/from the seawater side of the H/E will be affected.


As for the seawater pump, did you inspect the impeller cam?
As well as the impeller being correct for the pump body, the cam is equally as important.



.
 
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Ricardo,
Thanks for the response. I beleive that the gaskets/block off plate were correct and installed per the Crusader manual diagram. If I recall correctly, there is a three slot gasket, block off plate then a one slot gasket between the manifold and riser and a one slot gasket between the riser and elbow. Is there any way to check for an obstruction without taking the whole this apart again?

With respect to the pump all the parts appeared to be fine even the impeller but since I has it apart, I thought it was best to go ahead and install a new impeller.
Regards
Ned
 
Ned................
Ricardo,
I beleive that the gaskets/block off plate were correct and installed per the Crusader manual diagram.

If there is a block off plate/gasket, then you have what's called a "full system".... meaning that the manifolds are included in the closed cooling system loop, and that only the elbows are seawater cooled.
Depending on how the risers/spacers are installed and configured, the block off plate/gaskets could be above or below the risers/spacers.

If you do not have a Full System, then all ports must be fully open.

Side note regarding a Full System:

Spacers/risers are typically installed between the manifold and elbow. They can be used to elevate the elbow, or can be used to provide porting.

Depending on the system, manifold porting and elbow porting......, spacers/risers may be within the closed cooling loop, or may be in the "spent" seawater loop.
This determines where the block off plates/gaskets install.


.
 
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Thanks Ricardo,
The block off plate is located at the bottom of the riser between the riser and manifold. The manifolds are a part of the closed cooling system so I beleive that it is a full system.

The raw water exiting the heat exchanger is dumped into the bottom of the riser and exits from there so I beleive that the risers and elbows are seawater cooled. I have attached a picture of the riser taken from the marine parts website.
Regards
Ned
Crusader 97772 4 inch Exhaust Riser - Big Block End Style - Crusader Exhaust_Page_2.jpg
 
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