My 50 HP Perkins (1980 model) has been acting up and seems to bog down immediately. The performance of the engine as decreased over the last 6 months. The temperature guage goes to redline and I don't seem to be making any headway - 4-5 kts at full throttle. I just had a mechanic look the boat over (sea trial) this afternoon and he said the water intake wasn't blocked and the engine seemed to be running correctly. A new water pump was installed and the intake is clear. There are no coolant leaks either. He suggests taking out and cleaning (or replacing) the heat exchanger. It this a good idea? Estimated charge $1,000+. If this is the problem, does anyone know where to find a mechanic near Tarpon Springs/Clearwater, FL that charges less than $100 per hour. Thanks.