Low engine temps

A

ALKA2710

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Joined
Mar 5, 2007
RO Number
25407
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670
8.1L mercruisers fresh water cooled have been running at a 140 degrees since I bought the boat last year. Figured wrong thermostats in and would be a quick change since it calls for 160's. Took out the first thermostat and too my surprise it was a 160. Figure the other one is the same. Any ideas why she would run cooler than the thermostats that are in there. Should I put 170s in and see if it raises the temp.
Al

Al
 
Al,

Like Mike said, 140 according to a gauge or according to, say, an IR thermometer?

V/R
 
I am going to put a gauge on her tomorrow but find it kinda weird that both gauges would read the same temp wrong. Manifolds stay very cool. Would describe them as warm not hot.
Al
 
Just so I know where should I aim the IR thermometer to get the best reading. I would guess top of thermostat housing
 
There's a sending unit at the top of the thermostat housing. Actually, there's a couple. Use a specific spot to check temps. You can check around and find different readings on the same housing depending on if it's on the inflow coming from the heat exchanger(cool water) or going to the heat exchanger(hot water). Exhaust manifolds are generally pretty hot and the risers can be luke warm.

and as long as you have a temp gun, check the oil pan after a run...but then again, I wouldn't want to freak you out.
 
Charlie you freaked me out. Can you explain the oil pan theory to me. Thanks
Al
 
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