Honda BF75L cooling water issues

[Cpotts]

I've got the same problem on my 1983 BF75L. telltale is decently strong, but the water is really hot after about 1 minute. After 2 or 3 minutes the engine dies. It's in a big bucket with water level nice and high.
I removed the inlet manifold and there's no thermostat! and it's pretty dry in the housing. I'm guessing water isn't reaching entire water jacket and it's overheating.
I was trying to trace the water pathways and using my compressor to blow them out. looking at the manifold itself, I don't see a pathway for water to even get to the thermostat.
I need help figuring out why the thermostat pathway is dry and how is water supposed to get there in the first place..

 

[Cpotts]

Water seems to flow down the curved galley in the manifold. that leads directly to the tell tale as far as I can see. Flow from the tell Tale is pretty good.
looking for help determining the water pathways. As far as I can tell, water never reaches the thermostat housing which doesn't make.sense

 

[flashback]

There are two circuits from the pump, the tell tail is simply a telltale. The other circuit is doing the actual cooling.. maybe this will help...

 

[Cpotts]

thanks flashback...that helps. the confusing part is that the thermostat seems to be housed moreso in the inlet manifold than the cylinder head.
and if I'm hearing you right, the telltale just indicates that the pump is working. it doesn't really participate in the cooling? it does get quite hot

 

[Cpotts]

also, the previous owner was running it without a thermostat. so water should be getting everywhere...technically I shouldn't be overheating.

Maybe they took the thermostat out when they couldn't solve the overheating issue?

I'm still a bit confused with the thermostat housing. Upon inspection there's a single hole on the block side of the thermostat housing. so I'm not sure how it facilitates the flow of water. would there be a way for water to flow through the thermostat??

 

[flashback]

You have the gist of it, the thermostat holds water in the block until the temp opens it up, then the hot water is released to the exhaust. You probably should get a thermostat. I think cool water is just moving thru the engine without the thermostat and passing hot water thru the telltale the way it is now..

 

[Cpotts]

I can't see how the thermostat releases water to the exhaust.
it's housed mostly in the block, and partially in the inlet manifold
there's a water pathway to the thermostat on the block side. (see first pic).
If hot water from the block reaches the thermostat, it would open. But there's nowhere for the water to go. the inlet manifold side of the thermostat housing has no opening (see second pic) . Just nooks and crannies leading to dead ends.

 

[flashback]

You're lost me but maybe this will help you

 

[racerone]

Cpotts----Honda builds lots of engines and I am sure these thermostats work just fine.

 

[Cpotts]

Cpotts----Honda builds lots of engines and I am sure these thermostats work just fine.

I'm sure they do too... I'm just not seeing it

 

[flashback]

I think that what you don't see is if the thermostat is not there the water just flows freely thru the motor and offers very little cooling..

 

[Cpotts]

Cpotts----Honda builds lots of engines and I am sure these thermostats work just fine.

You're lost me but maybe this will help you

truly appreciate your help flashback...let me explain a bit better...
the thermostat essentially closes a water pathway, then opens it when the temp rises.
A water pathway would have two holes- a path in, and a path out .

inspecting this engine I can only see a single hole. so when the thermostat opens where does the water flow?

I'm missing something....

 

[Cpotts]

I think that what you don't see is if the thermostat is not there the water just flows freely thru the motor and offers very little cooling..

I wish there was water flowing through the engine ....it's bone dry on the thermostat housing . I've got a blockage somewhere just trying to figure out the pathways so I can locate the blockages

 

[flashback]

If you look at the diagram I posted you will see the fresh water goes directly to the block and excess goes to the telltale.. when the water in the block reaches operating temperature the thermostat opens an allows the water into the head and then out the exhaust..

 

[flashback]

The intake is always cooled by the excess and that's good..

 

[Cpotts]

If you look at the diagram I posted you will see the fresh water goes directly to the block and excess goes to the telltale.. when the water in the block reaches operating temperature the thermostat opens an allows the water into the head and then out the exhaust..

yes the first diagram made sense except the thermostat. it should be located on the left side of the cylinder head and it should extend into the inlet manifold. the

The intake is always cooled by the excess and that's good..

 

[MattFL]

Remove the thermostat housing and fire it up. You'll know pretty quick if water is reaching the thermostat. Have you checked the impeller and water pump in general to be sure it's in good shape?

If the thermostat is missing, I'm going to guess the previous owner had some sort of overheating problem and remove the thermostat to try to "fix" it, but the actual problem still exists. If it's an old engine that you're not really wanting to disassemble, I would try giving it a descaling flush with something like Rydlyme. IF The problem is calcium type buildup, that stuff (or similar) dissolves it. I did this to my old 99' motor and got a pile of what looked like beach sand out of it, I posted info on a thread here somewhere. Anyway, if the problem might be clogged cooling passages, then that might possible help.

 

[Cpotts]

You're lost me but maybe this will help you

I think my engine is slightly different than the one in the diagram. 1)

Remove the thermostat housing and fire it up. You'll know pretty quick if water is reaching the thermostat. Have you checked the impeller and water pump in general to be sure it's in good shape?

If the thermostat is missing, I'm going to guess the previous owner had some sort of overheating problem and remove the thermostat to try to "fix" it, but the actual problem still exists. If it's an old engine that you're not really wanting to disassemble, I would try giving it a descaling flush with something like Rydlyme. IF The problem is calcium type buildup, that stuff (or similar) dissolves it. I did this to my old 99' motor and got a pile of what looked like beach sand out of it, I posted info on a thread here somewhere. Anyway, if the problem might be clogged cooling passages, then that might possible help.

I'll definitely try and flush it...
I can't run it with the thermostat housing off. the housing is integrated into the intake manifold which also facilitates the fuel/ air mixture

 

[flashback]

That diagram came from an old factory manual I have lying around from 1979..

 

[Cpotts]

That diagram came from an old factory manual I have lying around from 1979..

thanks...I think they must have changed a bit by 1983