I have an outboard also (Johnson 130) on my H180. My temp gauge never moves either, but I attribute that to a broken wire on one of the temp sensors on the motor. There are two - one on each bank of cylinders. Unfortunately, new sensors are around $150 each!
Here is what my sensors look like. It's the tan wire that is broken just inside the sensor head...
So, I continue to run but I'm always checking to make sure I have a steady stream of water coming out of the cowling. I'm not sure what that port is called, but it's a small, steady stream of water that verifies you have flow thru the motor.
On the speedo gauge, if it isn't working, then it's most likely the pitot tube.
Looks like this and is mounted on the bottom of the transom: https://www.amazon.com/Pitot-Tube-Marine-Speedometer-56973P/dp/B00YMT398U
It could be cracked, clogged, broken hose going to it... any number of things. When you replace it, I would also disconnect it at the back of your speedo gauge, then blow thru the hose to make sure it's clear. Do NOT use an air compressor on this tube! Just have someone at the dash end listening for air to come thru. If it's clear and you have a new pitot installed, then your gauge may have other issues.
Hope this helps.