I've come to the conclusion that some independence and redundant sources of temperature information plus a bit of work to insure what I have works correctly before making any changes is the most prudent course.
Thanks again!
I think you have come to the correct conclusion. Also, your alarm should be set to 203 as per Cummins and not 190. As everyone has stated, 190 is not particularly "alarming" as far as temp goes. You just don't want it to go any higher than that.
I have 330Bs in my boat and have had similar issues. I do not know the "flow diagram" of your exhaust system but I would think the first spot your impeller vanes would get hung up is your transmission cooler since you do not have an aftercooler.
As far as Murphy Gauges go...I did purchase one. They are mechanical extremely accurate gauges. I used it as a compliment to make absolutely sure all of my other indications were correct(OEM gauge and IR gun). I screwed it into the port where the temp sender is. And that confirmed to me that my engine was NOT running as hot as indicated.
My issue with IR guns is that you can hit one spot(ie near temp sender) and it show 178. Then move it a millimeter and it shows 243. That is a just an example but you can basically get whatever temp you want out of it based on where you point it. I guess my point here is I do not get a lot of confidence out of the reading of an IR gun. My most consistent temps are on the pipe leading to thermostat and on the expansion tank. I was told to hit the beam at the head just right next to the sender. I cannot get a consistent reading there.
Anyway, a Murphy gauge is cheap and easy to use and will answer a lot of questions for you....mainly is your gauge correct.
I even went so far as getting another heat exchanger(I am not advocating this....only exemplifying how far I was willing to go to get to the bottom of the issue). It is not installed but I was damn curious....$860 curious....and that is not OEM parts. The OEM Cummins part was something like $1800. A Company called Mr. Cool sells them cheaper and they are made by the same people....Sendure and...I forgot the name of the other one. Very excellent customer service people at Mr. Cool.
So Ski and David, I have a question. When I took the sending unit out of the hole and screwed in the Murphy Gauge, was I also disconnecting the alarm??? IOW, is the alarm on the same wiring/circuit as the gauge??? I assumed it was and acted accordingly. ANd I never saw anything over 185.