I bought a bass tracker txw175 last year with a Mercury 50HP ELPTO. The water output was never the best but was always suitable to keep the engine cooled. After setting up a couple months, I took boat out the other day and started after fishing some brush piles close to ramp. Water would come out of pee hole when idling but not when engine reved up. I shut engine down and loaded. Hooked up muffs at house to force water through and it did the same thing as on the water. The motor doesn't have 20 hrs on it. Could it be the impeller already needs replaced? We did check to see if it was stopped up and the line is clear. No debris or dirt daubers. Any help would be greatly appreciated!