Quote Originally Posted by 5:00 View Post
1. The water temp is 54 degrees and I am seeing the gauge at the normal 179 degrees. It seems a bit high with water that cold but maybe ok?
2. The thing that is worrying me a bit is it will drop down 20 degrees from that 179 to about 159 in about 5 seconds. Is it possible for the temp to drop 20 degrees in 5 seconds? It will stay at 159 then go back up again whenever it feels like it. All of this while not changing what the boat is doing.

Any ideas what might be going on?
It's not overheating but it is strange.
Your gauge and thermostat are working perfectly. The temperature of the water will not change the normal operating temp of the motor. The thermostat will open when it needs to in order to cool the engine. With water very cold you will see a quick change in the temp (especially if the sensor is in an area that picks up the temp from coolant as it is introduced into the engine. After a drop you will see the temp slowly climb as the thermostat closes again. Then it opens again and you see a repeat.

It is not nearly as dramatic on a hot day when the thermostat mostly stays open and the water temp is not so cold.