cooling on Johnson 1979 150hp

R

rlouis5

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Sep 15, 2011
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the motor does not seem to run too hot (157 degrees with a digital thermometer ) and the pee water is strong...but no water comes out the two holes on the leg of the motor..I also have a 1978 175hp that has a good stream coming out of these two holes ...not hot but runs at a max of 130 degrees...I am wondering if I need to replace both thermostats on the 150 to get water out of the leg?????
thank you
Robert
 
B

boobie

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Re: cooling on Johnson 1979 150hp

At what rpm are you taking these temps at ??
 
R

rlouis5

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Re: cooling on Johnson 1979 150hp

taking these temperatures at idle after about 5 minutes...I have replaced both thermostats and everything looked clean in there...still no water flow out of the leg but a good strong stream out of the tell tale.
 
E

emdsapmgr

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Dec 9, 2005
Messages
11,551
Re: cooling on Johnson 1979 150hp

New stats should open at 143 and run close to that on the garden hose. When the engine is in a warm lake in august, it may get up to 150/155 at idle. The 157 is on the high side of normal. 130 is pretty low. You'd be better off verifying with a laser temp gun on the heads. If you can't borrow one, you can rent one for the day from most auto parts stores.
 
R

rlouis5

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Messages
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Re: cooling on Johnson 1979 150hp

these temperatures were taken with a laser thermometer ....I cleaned the water inlets from the thermostats down with a weed trimmer line as far as I could get it to go on each side ...the left side ( from the back) has a small amount of water coming out now and the right side has only a little drip coming out...the temperatures did drop to about 145 max..
thank you again
Robert
 
E

emdsapmgr

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11,551
Re: cooling on Johnson 1979 150hp

Have you thought about pulling the head covers off to inspect the cooling passages in the heads? (you don't have to pull the heads...)
 
R

rlouis5

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Re: cooling on Johnson 1979 150hp

no...I did not even know that it was possible to remove the covers on the heads....does it take new gaskets? Do you think it is possible for a novice to preform this task? Or would it have to be taken to a boat repair shop?
thank you
Robert
 
E

emdsapmgr

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Dec 9, 2005
Messages
11,551
Re: cooling on Johnson 1979 150hp

You can pull the covers off. New gaskets will be required, but they are probably inexpensive since they are just a common paper type gasket. Be careful-if the covers have never been off, you could have problems getting the 1/4" bolts out in one piece. What you find in the passages of the heads you will probably also find inside the cylinder cooling passages.
 
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