Alright, searched a little and couldn't find a lot of info. Took the boat out today, outside temp around 70 water around 57 or so. Engine seemed to stay around the 140 - 160 range at idle. (Usually runs 160 normally) but when I would cruise across the lake it would drop, one time all the way down to 100, which is the bottom of the gauge.

I replaced the thermostat last year, could it be bad again? Stuck open, maybe? Any other ideas?

Let me know your thoughts. Thanks.