Normal Operating Temperature for a 3.0 mercrusier??

[MuskyHuntr]

I was wondering what the normal operating temperature should be on a 3.0 Liter mercrusier 140hp stern drive?

I have a little less than 145 degrees running at 1000 RPM.. Matter of fact I trolled all day on Saturday (like 12 hrs) at 1000-1100 rpm and the temp gauge never moved from that.. Picked up and ran in running 3000 rpms for approx 15 to 20 minutes and the temp gauge rose to 175 degrees...
Is this normal or is there something wrong? Should it be approx. 145 degree's all the time.. ????

any input would be greatly appreciated..

Thanks
Mark