Temperature readings in the engine room (clamshell).

[electricjohn]

I installed 4 thermocouples in the engine room and took readings while underway, stopped, engine turned off for a few minutes, then a half hour later.  Underway, all 4 t-couples read 115 F. Stopped temps went from 115 to 125 within a minute blower or not.  Once parked temps went to 130 and stayed there for the next half hour.  2 T/C's were mounted low and two were mounted high, both front and rear of engine.  Surprisingly temps did not vary due to location and running blower had zero effect on cooling. 

[justgary]

24 minutes ago, electricjohn said:

I installed 4 thermocouples in the engine room and took readings while underway, stopped, engine turned off for a few minutes, then a half hour later.  Underway, all 4 t-couples read 115 F. Stopped temps went from 115 to 125 within a minute blower or not.  Once parked temps went to 130 and stayed there for the next half hour.  2 T/C's were mounted low and two were mounted high, both front and rear of engine.  Surprisingly temps did not vary due to location and running blower had zero effect on cooling. 

That's very interesting.  I guess that's why the blower trick doesn't really cure vapor lock like opening the hood does. 

I'm surprised it's that low underway.

[John I.]

Interesting. While underway, was your engine temp gauge showing ~160 F?  What was the outside air temp?

[UWSkier]

What was the ambient temp?  I'm a bit surprised at 115F underway.  Figured it'd be closer to ambient with the volume of air the engine pulls.  Do you have an insulated motor box?

[electricjohn]

Ambient was mid 80s and clamshell is insulated.  My intake air is fed to the bilge thru 2- 3" flex hoses. ECT was 160 and heat soaked by a long ride. Boat speed had no effect on temps either.