Re: overheating
Yes you do have a thermostat, you may also have a blockage between the pump and the powerhead. I am sure that some real experts will chime in, but I do not believe that you have a tell tale on a 74 135hp so you would not see a stream of water coming out. The two holes in the mid section should spray water though. You really need a manual before you get to far in the engine. Hope this helps until you can get some better advise.