I have a 1988 350 mercruiser that I had longblock replaced, had it out this weekend and it ran great. I know temp guages are inaccurate, but undreway it stayed right at 160, when I slowed to approach a dock, i was idling and noticed guage rise to appx 175-180 stayed there and then slowly lowered to just over 160, normal? or am I paranoid after shelling out all that dough?