Just bought boat & the first time taking it out, the alarm went off. It had only ran approx 5 minutes, the temp light came on when trimmed engine 1/2 way. We turned it off & back on and no alarm. It only comes on when engine is trimmed half way. Put on a new impeller and still have the same issue. The water coming out is not hot. Any ideas? "the tach meter" does not work.