I am suspecting my boat's (1990 Ford OMC Cobra 2.3L) overheating
problem comes from a defective thermostat. Today, I replaced the
thermostat but the gasket that I was given does not fit the housing at
all so I had to reuse the old worn gasket for now. I started the
boat and it gradually went to over 200 degrees which means the problem
is not fixed. I also noticed that steam was coming out of the
thermostat housing around the old gasket. So obviously I don't have a
100% seal and I will need to find the proper gasket.

However, I am wondering if the leaking gasket would be enough to
cause the new thermostat not to work or if I simply misdiagnosed the
problem in the first place and will have to look somewhere else?

Impeller and water pump was replaced 2 months ago so I don't think
this is the cause. Will have to also check the hoses and the water
intake I suppose.

Andre

Melandre wrote:
I am suspecting my boat's (1990 Ford OMC Cobra 2.3L) overheating
problem comes from a defective thermostat. Today, I replaced the
thermostat but the gasket that I was given does not fit the housing at
all so I had to reuse the old worn gasket for now. I started the
boat and it gradually went to over 200 degrees which means the problem
is not fixed. I also noticed that steam was coming out of the
thermostat housing around the old gasket. So obviously I don't have a
100% seal and I will need to find the proper gasket.

However, I am wondering if the leaking gasket would be enough to
cause the new thermostat not to work or if I simply misdiagnosed the
problem in the first place and will have to look somewhere else?

Impeller and water pump was replaced 2 months ago so I don't think
this is the cause. Will have to also check the hoses and the water
intake I suppose.

Andre

It may be OK for a pressurized cooling system to run at 200 degrees.
What does your OM say? However, if you have steam leaking out from
around the thermostat gasket you don't have proper pressurization and
that will lower the boiling point of your coolant substantially.

This is not a closed cooling system just a standard cooling system
where the boat draws sal****er from the ocean. The manual says that
the thermostat should start opening at a temp of 160F and be fully
opened at around 180F.

I plan to remove the thermostat housing (and the new thermostat) and
reassemble the housing without a thermostat in it. This should allow
me to determine if the problem is the thermostat or not. Without a
thermostat, I am assuming that cooling water is drawn all the time so
in therory, the boat should not overheat. If it does, it probably
means that the problem is elsewhere (plugged hose, riser, water pump,
impeller, etc..)

A.

On 17 Aug 2005 21:26:53 -0700, wrote:


Melandre wrote:
I am suspecting my boat's (1990 Ford OMC Cobra 2.3L) overheating
problem comes from a defective thermostat. Today, I replaced the
thermostat but the gasket that I was given does not fit the housing at
all so I had to reuse the old worn gasket for now. I started the
boat and it gradually went to over 200 degrees which means the problem
is not fixed. I also noticed that steam was coming out of the
thermostat housing around the old gasket. So obviously I don't have a
100% seal and I will need to find the proper gasket.

However, I am wondering if the leaking gasket would be enough to
cause the new thermostat not to work or if I simply misdiagnosed the
problem in the first place and will have to look somewhere else?

Impeller and water pump was replaced 2 months ago so I don't think
this is the cause. Will have to also check the hoses and the water
intake I suppose.

Andre

It may be OK for a pressurized cooling system to run at 200 degrees.
What does your OM say? However, if you have steam leaking out from
around the thermostat gasket you don't have proper pressurization and
that will lower the boiling point of your coolant substantially.

If you want to see if the thermostat is bad - toss the old one in a pan
of hot water on your stovetop and see if it opens when it reaches the
desired temperature (use a candy thermometer to test the water temp if
you need to). Normally, exact temps don't matter - the stat will ether
pop open when the water starts getting really hot, or it'll never pop
open if its bad, but sometimes they are just slow (and tus the candy
thermometer is a good tool)

Just because the impeller was replaced 2 months ago doesn't mean it's OK.
Put the boat in the water and pull the hose from the outdrive and briefly
start the engine. It should pump a lot of water. You should know in under 1
minute. Also since you have run the engine HOT you may have done other
damage such as headgasket, etc.


"Melandre" wrote in message
...
I am suspecting my boat's (1990 Ford OMC Cobra 2.3L) overheating
problem comes from a defective thermostat. Today, I replaced the
thermostat but the gasket that I was given does not fit the housing at
all so I had to reuse the old worn gasket for now. I started the
boat and it gradually went to over 200 degrees which means the problem
is not fixed. I also noticed that steam was coming out of the
thermostat housing around the old gasket. So obviously I don't have a
100% seal and I will need to find the proper gasket.

However, I am wondering if the leaking gasket would be enough to
cause the new thermostat not to work or if I simply misdiagnosed the
problem in the first place and will have to look somewhere else?

Impeller and water pump was replaced 2 months ago so I don't think
this is the cause. Will have to also check the hoses and the water
intake I suppose.

Andre

Melandre wrote:
This is not a closed cooling system just a standard cooling system
where the boat draws sal****er from the ocean. The manual says that
the thermostat should start opening at a temp of 160F and be fully
opened at around 180F.


If I read that last sentence literally, it is simply describing the
operation of the thermostat and not the recommeded operating temp for
the engine. There is no reason the engine coolant temp could not or
should not rise above the temperature at which the thermostat is fully
opened.

I'd be surprised to discover that you truly have raw water cooling. Are
you sure you don't have two coolant circuits on your engine? One
comprised of
fresh water and antifreeze that circulates through the block and heads
(after the thrermostat opens of course) and the other the raw water
flow that is pumped through your heat exchanger to extract the heat
from the engine coolant (and often through the exhaust manifoolds or
risers) before carrying the extracted heat out through the exhaust
hose?

However, as you are operating in salt water, it is better to keep the
engine coolant temp down to about 190 or less. At about 190 degrees,
the suspended salts begin separating from seawater and will begin
building up
in your cooling circuit. Not a good thing.




I plan to remove the thermostat housing (and the new thermostat) and
reassemble the housing without a thermostat in it. This should allow
me to determine if the problem is the thermostat or not. Without a
thermostat, I am assuming that cooling water is drawn all the time so
in therory, the boat should not overheat. If it does, it probably
means that the problem is elsewhere (plugged hose, riser, water pump,
impeller, etc..)

A.

On 17 Aug 2005 21:26:53 -0700, wrote:


Melandre wrote:
I am suspecting my boat's (1990 Ford OMC Cobra 2.3L) overheating
problem comes from a defective thermostat. Today, I replaced the
thermostat but the gasket that I was given does not fit the housing at
all so I had to reuse the old worn gasket for now. I started the
boat and it gradually went to over 200 degrees which means the problem
is not fixed. I also noticed that steam was coming out of the
thermostat housing around the old gasket. So obviously I don't have a
100% seal and I will need to find the proper gasket.

However, I am wondering if the leaking gasket would be enough to
cause the new thermostat not to work or if I simply misdiagnosed the
problem in the first place and will have to look somewhere else?

Impeller and water pump was replaced 2 months ago so I don't think
this is the cause. Will have to also check the hoses and the water
intake I suppose.

Andre

It may be OK for a pressurized cooling system to run at 200 degrees.
What does your OM say? However, if you have steam leaking out from
around the thermostat gasket you don't have proper pressurization and
that will lower the boiling point of your coolant substantially.

No, it is (unfortunately) just a standard cooling system (it is only
17.5' boat). Simply put, recently the boat starts hot (needle creeps
to the 200F to 250F range) and after a random period of time (averaging
1 to 4 minutes) needle suddenly drops to around 150F and all is well
and engine appears to stay at approx. 150F.

If it was the impeller or clogged hoses, wouldn't the problem continues
after 3-4 minutes of running? Andre

Melandre wrote:
No, it is (unfortunately) just a standard cooling system (it is only
17.5' boat). Simply put, recently the boat starts hot (needle creeps
to the 200F to 250F range) and after a random period of time (averaging
1 to 4 minutes) needle suddenly drops to around 150F and all is well
and engine appears to stay at approx. 150F.

If it was the impeller or clogged hoses, wouldn't the problem continues
after 3-4 minutes of running? Andre

If you are dropping back to 150 degrees after an initial heat up to
200-250 degrees, it does indeed sound like the thermostat. Impellers,
hoses, obstructions, etc are permanent situations, not self correcting.

If you test the thermostat in a pan of water, (using a candy
thermometer to note the temperature at which it is opening), and it
appears to be opening within specs you might need to go to a thermostat
with a lower rating. There's no good reason to heat up to 250 degrees
if your engine is happily running at 150.

Good point about the impeller. I am quickly findig out that in boating
one should not take anything for granted (except that it will cost us
a lot of money!). Today, along with a proper gasket for the
thermostat housing, I also bought a new impeller (just in case, if
fine then I'll have one as a spare for next year).

I'll be back at the marina after work tomorrow night to see if putting
a proper gasket on the thermostat housing makes a difference (ie was
that enough to cause the new thermostat not to work yesterday when I
replaced it). A.




On Thu, 18 Aug 2005 10:40:50 -0400, "Woodchuck"
wrote:

Just because the impeller was replaced 2 months ago doesn't mean it's OK.
Put the boat in the water and pull the hose from the outdrive and briefly
start the engine. It should pump a lot of water. You should know in under 1
minute. Also since you have run the engine HOT you may have done other
damage such as headgasket, etc.


"Melandre" wrote in message
.. .
I am suspecting my boat's (1990 Ford OMC Cobra 2.3L) overheating
problem comes from a defective thermostat. Today, I replaced the
thermostat but the gasket that I was given does not fit the housing at
all so I had to reuse the old worn gasket for now. I started the
boat and it gradually went to over 200 degrees which means the problem
is not fixed. I also noticed that steam was coming out of the
thermostat housing around the old gasket. So obviously I don't have a
100% seal and I will need to find the proper gasket.

However, I am wondering if the leaking gasket would be enough to
cause the new thermostat not to work or if I simply misdiagnosed the
problem in the first place and will have to look somewhere else?

Impeller and water pump was replaced 2 months ago so I don't think
this is the cause. Will have to also check the hoses and the water
intake I suppose.

Andre

Melandre wrote:

I am suspecting my boat's (1990 Ford OMC Cobra 2.3L) overheating
problem comes from a defective thermostat. Today, I replaced the
thermostat but the gasket that I was given does not fit the housing at
all so I had to reuse the old worn gasket for now. I started the
boat and it gradually went to over 200 degrees which means the problem
is not fixed. I also noticed that steam was coming out of the
thermostat housing around the old gasket. So obviously I don't have a
100% seal and I will need to find the proper gasket.

However, I am wondering if the leaking gasket would be enough to
cause the new thermostat not to work or if I simply misdiagnosed the
problem in the first place and will have to look somewhere else?

Impeller and water pump was replaced 2 months ago so I don't think
this is the cause. Will have to also check the hoses and the water
intake I suppose.

Andre

Automotive thermostats regulate engine temp above STP boiling,
requiring a pressure seal. Boats do not, as high temps apparrantly
cause scaling in raw water. Use a low temp t'stat, about 180 or so,
I believe.

If you want to see the someplace else, run the engine with no
thermostat. How hot now?

Terry K