I just changed the prop on my 89 Johnson 60 HP. Shakedown cruise was going great until I increased RPM's to 44-4500. The overheat alarm went off within 20-30 seconds and the SLOW circuit engaged. Motor idled 20-30 seconds and overheat alarm went off. I thought maybe the thermostat was stuck and tapped the housing to free up. Ran motor again and had the same problem. Ran back to the landing at 35-4000 RPM without a problem. Until this alarm, the motor had been running great.The new prop is a Michigan Wheel 13 3/4 x 15, same as the old prop but stainless instead of aluminum. Impeller was last changed approximately 1 year ago, thermostat changed 4 weeks ago. Motor ran great 1 week prior and throughout the Winter/Spring. Any ideas? Anyone seen a prop change cause a problem like this?
