Normally, the 9.5’s don’t spray a lot of water out the back until the motor warms up and the T-stat opens up. Then it gushes out. This is the same for the early 9.9/15 horse motors. If the motor is idling in a barrel, it might not be be generating enough heat to open the stat so making some horsepower by putting it in gear and revving it up a bit should heat it up enough to open the stat.
At lower speeds, you will see the water outflow fluctuate as the stat opens and closes. At higher speeds, the flow should be steady.
One symptom of a stat which is stuck open is poor extended idling and wet or fouled plugs as the motor can’t get hot enough to burn off the oil.
Some bad stats.
And this beauty, which I found being sold on Ebay for a premium price.
