After warming up, my Volvo D4-300 engine temp runs constantly at 185, unless I run near or at WOT. At near or WOT, the temp suddenly jumps to 195-197, then settles back to 185 when I back off a few hundred RPM.
I was so concerned about this that I questioned the Volvo certified mechanic that I use from Diversified Yacht Services in Fort Myers Beach, FL. He told me that, with the temp gauge being totally electronic, Volvo was able to purposely manipulate the displayed temp to always be 185, even though the actual coolant temp in practice does vary from 185 under normal cruising conditions. Their approach is if the actual coolant temp rises above a certain threshold it jumps to that new actual temp on the gauge, otherwise the gauge simply shows 185. Same type of threshold jump occurs when the actual temp falls a certain amount.
I asked why Volvo took this approach in displaying coolant temp. He stated that they primarily do that to eliminate a lot of the worries and questions from customers about what is a reasonable temp, ESPECIALLY with twin engine boats. With twin engines, many customers seem to think their coolant temps should be identical. If they are off from each other by only a couple of degrees, the customers think something serious is wrong.
He then told me to run WOT periodically to see what happened on the gauge. If it simply jumped to 195-197 then stayed there until backing off on the throttle, all was okay. If it continued to rise above 195-197 at WOT, then there is likely a problem with a water flow issue of some type - partially plugged sea strainer, or partial obstruction in the heat exchanger, etc. When I do as he asked, I get exactly the results that he predicted. So, I have concluded that I have no raw water obstruction issues.
CAUTION: Although I got this information from a certified mechanic, it did NOT come from the Volvo factory or their factory representative, so take it for what it is worth!
