I have a very weak telltale stream after I changed my impeller so I took out the t-stat to see if that was the problem. The stream was much stronger with the muffs and hose. The t-stat has no corrosion on it and I was wondering if it is still good. It’s in the closed position but all of the parts move freely. Could it be that the motor isn’t getting hot enough to open the t-stat even after long runs on the lake at wot, or do I just need to replace the t-stat.