MD7B runs hot when the water
heats up in the summertime in Texas
(very hot right now). My temperature guage only has green and red, no numbers, so I don't know exactly what the temperature is, but it will come up to the red and usually stop right there as long as I keep the rpm's down. It has gone up into the red a little bit, but not too much.
It has a 180 degree thermostat on it and when its running cool, you can see the thermostat open and close on the temperature guage. At that point, the needle on the guage is about 1/4 inch from the red zone. So I'm guessing that the red zone probably starts at about 200 degress. I run 50/50 water/coolant mix.
It has a Sen-dure fresh water cooling
kit on it. Its a 1983 boat and engine
and I bought it in 1993 and it had the fresh water cooling
on it when I bought it. As far as I know, it has always had the fresh water cooling system on it.
This has been an ongoing problem and I have been through the cooling system multiple times. I even had it "de-scaled" (flushed for 5 hours with rid-lime).
The accumulation tank and the heat exchanger
get hot to the touch. Both pumps have been serviced and are working good. It has good raw water
flow through the exhaust
Having not been able to find anything wrong, I am wondering if the heat exchanger
is too small. This heat exchanger is for an MD7A engine
. Sen-dure doesn't have one for the MD7B. The MD7B is a 17hp engine vs. 13hp for the MD7A. They both have the same block but the MD7B achieves more horsepower through higher rpms (3000). However, I don't run it that high. I keep the revs down in the summer.
If anyone has any experience or insight on this, I would appreciate your suggestions.