Just sea trialed my 30 and it runs like a clock. at sustained 2800 rpm for 30 min after long warm up the temp stayed at 160. I was expecting it to go to 180. Past engines have gone 180 dispite cold Maine waters. Is there an issue here?
You will be just fine. If you are correctly propped and you run the engine hard for a period (say at 3,600 for 20 minutes), you will find that the temp will increase to 180 to 195. The cooling system must be able to cope with this as with 100 degree temps and 85 degree water. When you slow down again the temp should return to 160 to 175.