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Temperature

the t-stat should be 160 deg F...and the sender unit is typically in the thermostat housing...so if its right, maybe 165 deg F is a decent target (as long as the sea water temp coming in is under 80 deg F...once it gets about that the HX is closed to being maxed out on its heat removing capacity.

what temps are you seeing? and did you purge the air out of the system once you put the exhaust system back together?
 
I did new risers and elbows. I have not filled heat exchanger yet. I was just wandering what is the high side for temperature would be with out causing damage.
 
ok...damage may occur when the high temp alarm occurs and thats between 200 and 210 (depending upon who's switch was used)...
 
Ok I filled heat exchanger with antifreeze, ran boat for an awhile. The temperature at thermostat housing got to 162 degrees but exhaust manifold got up to 178 degrees. At that point I turned boat off. The thermostat I don’t think opened cause antifreeze in heat exchanger did not go d for me to add more fluid. How hot can heat exchanger get ??
 
99% of the time, you will need to run a couple heat up - cool down cycles to purge the air from the cooling system....the manifolds and the heat exchanger will be a hotter than the t-stat opening point...how much depends upon the load on the engine.

I'd think you got close to opening the t-stat after the engine was shut off...check the level in the heat exchanger when it is cool and son't be surprised if it has dropped a good bit...refill and then repeat until the coolant level stops dropping...
 
makomark said:
99% of the time, you will need to run a couple heat up - cool down cycles to purge the air from the cooling system....the manifolds and the heat exchanger will be a hotter than the t-stat opening point...how much depends upon the load on the engine.

I'd think you got close to opening the t-stat after the engine was shut off...check the level in the heat exchanger when it is cool and son't be surprised if it has dropped a good bit...refill and then repeat until the coolant level stops dropping...
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How hot can I take the exhaust manifolds too before damaging something?
 
I'd say 210 deg F, on the manifold, where the cooling jacket is, would be a reasonable limit, with no load on the engine.
 
makomark said:
I'd say 210 deg F, on the manifold, where the cooling jacket is, would be a reasonable limit, with no load on the engine.
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Top of exhaust manifold is 180 degrees and the side of manifold is 160. With out a load. Going for a sea trial tomorrow and check again under load. Do those numbers seem close to being right ?
 
they are within reason....the inlet to the manifold should match the t-stat outlet and the outlet from the manifold will be hotter...the temp will vary with engine load and water flow ...
 
makomark said:
they are within reason....the inlet to the manifold should match the t-stat outlet and the outlet from the manifold will be hotter...the temp will vary with engine load and water flow ...
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The thermostat has not been changed in many years. Should I put a new one in now before I seatrial boat.
 
Went on sea trial this weekend. Everything went well, but the motor is still running a little hotter than it used to run. I think it maybe time to change thermostat. Will I lose much coolant when I remove the hoses from the housing??
I want to give a great shout out to MakoMark for all of his help. You helped me tremendously.ThaNK YOU
 
You are welcome...

On the coolant...a lot depends on your installed angle...figure anything above the thermostat should be drained below the level of the housing by at least an inch to minimize loss when the hoses are pulled...Most of the time, I find it easiest to drain both exhaust manifolds...and hoses with 'loops' or bends will have residuals below their high points...just enough to make a mess if you aren't expecting it...

Before you get into that, gotta ask when was the last time you had a new impeller in the raw water pump....and when was the last time it had the major service kit installed?
 
Just replaced impeller last month. The thermostat has not been changed in 22 years. It’s running about 10 degrees hotter than normal
 
ok...when was the last time the raw water pump had the major service kit installed?

there are other 'wear parts' that need to be changed to keep the pump working at max efficiency - the cam in particular. If it has noticeable wear, the pump won't deliver all of the water it is supposed to....

The other item is the HX - any idea if it has ever been checked/cleaned?
 
Temperature | Boat Repair Forum
makomark said:
ok...when was the last time the raw water pump had the major service kit installed?

there are other 'wear parts' that need to be changed to keep the pump working at max efficiency - the cam in particular. If it has noticeable wear, the pump won't deliver all of the water it is supposed to....

The other item is the HX - any idea if it has ever been checked/cleaned?
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i don’t believe it has been serviced. You think it’s the pump rather than the thermostat. It will run normal temp for first 8-10 miles then it crepes up after that and stabilizes a little warmer than normal
 
It could be the pump....not saying that it is...could also be little things - sea cock not open fully, strainer cap not fully seated, hose clamp on the suction side not fully tightened...as well as the cam or wear plate in the pump being worn...

If it runs 'normal' for "first 8-10 miles", to me that sounds like the t-stat is fine....and after the 10 miles, the temp crepes up because not enough heat is being removed thru the heat exchanger...which could be caused by the cooling water being marginal (volume) or if it gets aerated (not a solid flow of water)...

FWIW, keeping a log book, with all of the little maintenance details, can help tremendously in the future when sh*t happens again....
 
makomark said:
It could be the pump....not saying that it is...could also be little things - sea cock not open fully, strainer cap not fully seated, hose clamp on the suction side not fully tightened...as well as the cam or wear plate in the pump being worn...

If it runs 'normal' for "first 8-10 miles", to me that sounds like the t-stat is fine....and after the 10 miles, the temp crepes up because not enough heat is being removed thru the heat exchanger...which could be caused by the cooling water being marginal (volume) or if it gets aerated (not a solid flow of water)...

FWIW, keeping a log book, with all of the little maintenance details, can help tremendously in the future when sh*t happens again....
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Thanks I will check all the little things this week
 
One other question: when you did the elbows/risers, did you make sure the 'tabs' on the gaskets were in the proper position and the proper type (1-slot vs 3-slot)?
 
not usually...what do you mean by "...a lot faster..."?

Normally, cleaning the HX will allow it to transfer heat better to the cooling water...and that normally stretches out the time for the t-stat to open .... but not by more than a minute or two...
 
makomark said:
not usually...what do you mean by "...a lot faster..."?

Normally, cleaning the HX will allow it to transfer heat better to the cooling water...and that normally stretches out the time for the t-stat to open .... but not by more than a minute or two...
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The motor heats up much faster to 150 ish than my other motor. They used to rise about the same .
 
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