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J

John R. Daniels

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I have a boat that has 2 165 3

I have a boat that has 2 165 3.7 liter mercury engines. The engine temperature guages read arouind 195 degrees when warmed up. The temperature taken with a portable temperature guage in the coolant fill opening is always around 140 degrees. This is what it should be with the 135 degree thermostat.
Does anyone have any idea why this is.
 
"John...
Quite possible that

"John...
Quite possible that the temp sender in the engine, or the guage on the dash is inaccurate.

Wrench"
 
I did replace both of the send

I did replace both of the senders and both of the guages and the problem is still there .Unless either the new guages or the senders are faulty.. Both engines doing the same thing after new parts is what I do not understand.
 
get an inexpensive laser therm

get an inexpensive laser thermal temp. gun and check around the engine to see what temps. you get. Check right below the thermostat on the engine and see if it's 140 F.
 
"I'm having a very similar

"I'm having a very similar problem whith my 4.3. Temp with a portable unit is 135 or so. At the guage reaches 250+ but I'm still able to confortabley hold the sending unit in my hand immediately after removing it from the engine and there is no biling water coming out. I'll watch to see what folks recommend. I'm steering towards a wiring problem- ground, feedback, ??"
 
Run a ground jumper to each ga

Run a ground jumper to each gauge and see what happens. Are there warning alarms or idiot lights in the circuit? Disconnect them to see if they are the problem. Connect each gauge directly to the sender to bypass wiring; probably will need a 12 volt source.
 
Wouldn't the coolant in th

Wouldn't the coolant in the heat exchanger always be lower then the coolant in the engine? The coolant in the exchanger is always being cooled. The thermostat will only allow coolant to flow into the engine from the exchanger when needed (temperature in engine exceeds thermostat temperature. At least that's the way I always understood it.
 
"Capn Lazy...
I too had that

"Capn Lazy...
I too had that thought, but.... he's talking about a 55 degree temp difference and I was unsure if that much heat could be removed by that point in the system.

Wrench"
 
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