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#1
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what brand of water pump did you use, I've been burned before using aftermarket pumps. you can plumb in a garden hose y valve between the heat exchanger and the riser, run another hose off the y valve to dump overboard, while running, crack the valve leading to the over board discharge, if the temp starts going down, you have a restricted riser. Be careful, don't starve the exhaust of water or you'll burn the hose
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#2
08-20-2013, 07:35 AM
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Pump
I used Mercruiser parts.
On the muffs, I can't get the temp gauge over 120. In the water, temp gauge will stay at 120 at idle. At 2800 RPMs, I can run all day around 170 degrees. As soon as I bump the throttle to 3200, the temp will slowly rise to 200. If I open it up, it will quickly jump past 200 and boil. My recovery tank makes all kinds of noise...I am not sure if it's air or boiling coolant? If it's air, then I know it's the head gasket. My research tells me you can't find a small leak with a compression test because it's not enough pressure at low RPM's to find. Also, a leak down test may not work either. I don't want to pull the head and find it's something else. I do notice the riser gets hot as well as the heat exchanger. This still points to seawater not flowing fast enough?
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#3
08-20-2013, 10:45 AM
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It should be running hotter than 120 at idle and lower rpm. It sounds like a thermostat issue
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#4
08-20-2013, 11:50 AM
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Thermostat Issue
Does anybody know which way the thermostat drops in?
I have the older 470 with iron manifolds. I installed the thermostat with the springs down. If the thermostat is upside down, I am assuming it will cause a high speed overheat. Thanks for your help...
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#5
08-20-2013, 11:59 AM
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The spring should be facing the heated water.
A simple test to see if your t-stat is working properly: Take your stat and put it into a saucepan full of water. Bring the water to a boil. Remove the stat with a pair of tongs and look at it. Make sure it's fully open. Then, put a piece of string into the opening that occurred when the spring retracted due to the heat. Let the stat cool and capture the string. Then place the stat, suspended by the string, back into new, cool water and bring it to a boil again. Using a candy thermometer, measure the temp of the water as it's heating up. When the spring opens and the stat drops off the string look at the thermometer reading. That will tell you exactly what temp your stat is opening at. Check it against the reading stamped on the stat housing to see if it's within specs.
__________________
1987 V20 w/1987 150HP Yamaha on a Shoreland'r Trailer 1978 16.5 Airslot w/1996 120HP Force on a Four Winns trailer 1996 V21 w/1993 200HP Mercury on a Shoreline Trailer All towed by a 5.7L Hemi Durango. If God didn't have a purpose for us we wouldn't be here, so Live simply, Love generously, Care deeply, Speak kindly. (Leave the rest to God)  Silence, in the face of evil, is itself evil. Not to speak is to speak, not to act is to act. God will not hold us guiltless. Last edited by Destroyer; 08-20-2013 at 12:10 PM.
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#6
08-20-2013, 12:18 PM
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Spring facing the heated water
Then that tells me my thermostat is installed upside down.
The heated water is on top from the engine - the spring should face up in that case. Another thread showed the exact same thing. When the person fliped the t stat, everything ran great.
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