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Old 05-09-2019, 01:09 AM
Kevind1984 Kevind1984 is offline
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Tempature rising with Load. Help!!!

My struggle with my 1975 Atomic 4 engine continues. Ive now moved on to the cooling system. We idle at about 150 ish and the tempature starts to increase with load. at 2000 rpm it hits around 200 degrees and icreases with load. While trying to pinpoint the issue I went to test the thermostat and realized the previous owner must have taken it out and the engine has no thermostat. I ordered a new Thermostat and a new tempature sending Unit and matched stuart werner gauge from Moyer. In The meantime I acid Flushed the system , Bucket tested my flow rate, Flushed my heat exchanger and tested flow and refilled, replaced my impeller. Nothing helped. Where Else should I look? Any advice??
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Old 05-09-2019, 08:16 AM
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Removing the thermostat requires putting a restriction in the bypass to get cooling routed through the block. Without a restriction (usually a valve) the coolant bypasses the block and goes straight to the manifold.
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You should also examine the condition of the bypass spud on the underside of the thermostat housing dome. If it is eroded you will not realize the full potential of your new thermostat because of bypass leakage.
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1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Old 05-09-2019, 09:06 AM
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Al Schober Al Schober is offline
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First challenge is to get the temperature down. After you do that, you can get it back up where you want it. Remove the thermostat and close off the bypass (you can just pinch the hose with vise grips for a test).
If you have a heat exchanger, your problem my be clogged tubes or a problem with the pump on the glycol side of the system.

Last edited by Al Schober; 05-09-2019 at 09:09 AM.
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Old 05-09-2019, 10:31 AM
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The reason I am running RWC is that even with no thermostat and both pumps running, a hard run in warm water always had my temps around or past 180 with FWC. Now if you don't mind a hot boat and have no vapor lock issues, a FWC engine can run 200 all day no problems. The coolant won't boil until maybe 220 or so, maybe more.
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Old 05-09-2019, 07:46 PM
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Al Schober Al Schober is offline
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My experience is different from Joe's.
I added the heat exchanger, found out I needed a new coolant pump for the glycol (old Oberdorfer was leaking, installed the Moyer pump) and ran for several years with only one instance of overheating - forgot to open the raw water hull valve! This is with no thermostat installed. I had a bypass valve installed, but don't recall the degree of throttling - might have been closed. Anyway, running temps never got above 120F.
Should also add that I moved the temp gauge to the outlet of the manifold. The location at the fwd end of the head seemed to be reading head temperature rather that water temperature.
Did some research on head temperatures and found that the only folks monitoring head temp are the ultralight aircraft folk, air cooled. Their limits on head temp are on the order of 400-450F.
Kinda sorry to muddy the waters with temp sensor location, but I think it's important. I wanted to know the water temperature.

Last edited by Al Schober; 05-09-2019 at 07:50 PM.
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Old 05-09-2019, 11:05 PM
zellerj zellerj is offline
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Get a IR temp gun and shoot it around the block. Where is it hottest? The temp sender does not give you the whole story, so take temp readings of the head etc.

Could be that crude is wrapped around the cylinder walls from past sins. I could not control my temperature for 15 years, always ran about 210 F. I finally bit the bullet and took off the side plate, and found a lot of organic growth crusted around the cylinders. Cleaned that out with a pick and re-installed side plate - temp is now 140 F.

Since you did not have a thermostat, the path of least resistance from the coolant was to bypass the cylinders. If the cylinder walls are all insulated by crude, then the coolant will not do its job. You will see higher temps when this is the case.
Jim Zeller
1982 Catalina 30
Kelleys Island, Ohio
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