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MBL Engine Overheating

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francis

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"I have a 1939 Custom Runabout

"I have a 1939 Custom Runabout with an MBL. The engine was completely rebuilt last fall and I ran it several hours. It performed well, however it ran cool (120) I believe due to cold water in lake. I am now experiencing overheating. The water pump is new and checks out fine. There are no obstructions in the hoses. I have a new manifold and head on engine. I flushed water thru manifold. All plugs exhibit free flowing water. I removed temperature gage bulb from head and water flowed freely there as well. Engine normally ran at 140 degrees, now it rises under load above 180 degrees. Any suggestions appreciated."
 
"Jeff - Thanks for your reply.

"Jeff - Thanks for your reply. The engine does not have a circulating pump. However, I believe that the problem stems from the new water pump.ALthough it was bought recently, it appears to have wear. I spoke with the company that sold it to me and they were unable to tell me how they test the pumps. I don't believe that they test them at all! I am trying to find out the specifications on the water pump i.e. how much water it should be able to pump over time at a specific engine RPM. I appreciate help from anyone who might know this information."
 
"All I can think of, seeing yo

"All I can think of, seeing you don't have the usual circulating pump setup, is that the restriction orifice is missing.

Your setup requires a restriction in the line that bypasses the engine (from the raw water pump) or the water would not go into the motor. When the t-stat opens, the water is forced through the motor (easiest path) instead of by passing the motor.

Draw a diagram of what I'm saying and you'll see what I mean. THe restriction could be gone--rusted away--or left out.

Jeff

PS: You could always ADD an adjustable restriction in hte by pass line, using a globe valve. When it runs hot, you could clamp down a bit mor to force water through the block. Long as the valve never closes all the way it should do the job!"
 
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