I have a 1989 Johnson 175 (35 amp) that does not spark on the starboard bank when the rpm reaches 2700 or greater. As long as I keep the rpm below 2700 the engine runs fine. Can anyone tell me how to remedy this problem?
I disconnected the tan wire going to the temp switch on the port head and the engine now runs smoothly past 2500 RPM. Does this mean my temp switch is bad or is there another possible cause for the S.L.O.W circuit to limit the RPM on this engine?
Sounds like you found the problem. Check the sensor with ohm meter, should be open until about 206 degrees then close. If sensor closed when cold sensor bad. Sensor on port or stb head will set S.L.O.W.
When the engine was cold I checked continuity between the tan lead coming out of the temp switch and a good ground on the engine. I had zero resistance and when I switched the test probes I measured 500 ohms resistance. In both cases their was very little and/or no resistance and I would have thought it would have measured infinity (typical of open). Can you tell me why I had different resistance readings just by switching the test leads? Is their any trick to changing out the temp switch? Is their any after market switch comparable that is less than the $75 the dealer wants?
