Re: Water pump working?? '75 Johnson 115hp
Those 2 exhaust reliefs will have nothing coming out when the engine's idling cold, a little mist as she starts to warm up, and a heavy 'rain' when warmed up running at higher throttle openings. There's no telltale on that motor.<br /><br />There is a overheat alarm - either a horn in your control box, or a light on your dash. Check to make sure it's working. The heat sensor is on the starboard head, and has a grey wire going to it. There's a coupling about a foot up the wire from the sensor. Gently slide the black rubber boot off it, and ground the bare wire connector with the ignition turned on. Hear the horn? OK.<br /><br />There are plenty of Johnsons out there with 10yr old+ impellers, so don't panic. Nonetheless, impeller failure is one of the leading causes of death for those old motors, so put it on your to-do-soon list. In the meantime, watch the horn/light like a hawk, & keep in mind you may hurt the motor anyway. By the time the horn goes off, the motor can already be too hot (reason they put separate temp sensors on each head on the later-model V4s). If you don't change the impeller yourself, should be around 100-125 at a dealer. <br /><br />If the motor is cooling properly, the outside of the cylinder walls will be 125-140 degrees F (forget the exact number) when the motor is fully warmed up. You can leave your fingers on it for 2 or 3 seconds when it's that temp - so we're talking hot, but not enough to burn your fingers. If the motor's just a little warmer than the lake, your thermostat's either stuck open or been taken out. Those old single thermostat systems don't stick as often as the tiny twin thermostats they put in the 1978+ and newer motors, but it depends on how much saltwater the motors seen. I'd see to the impeller first for sure, unless the thermostat's stuck closed (they usually stick open). <br /><br />Carbs clean?
