thump/clunk after a few seconds in gear (1997 115 evinrude)
I just bought a boat with a 1997 115 evinrude. The motor runs great, but about 3-5 seconds into throttling forward I feel/hear a thump. It only does it one time (but not every time) after throttle up and then it runs flawlessly. It is an obvious mechanical thump that feels like when you shift sharply into gear at rpms higher than idle. It happens right in the middle of the run and does not affect motor speed.
Carbs are clean
Compression is 120 in all cylinders
water pump impeller is new
Lower unit oil was replaced (previous oil was pretty old, but practically no metal residue on the plugs)
One more thing... I was told by the previous owner that to operate the boat and get it into gear I would have to press and hold the button on the throttle box and move the throttle lever in the desired direction. However, if I move the throttle without pressing the button it goes into gear anyways and I have been operating it this way. I have not tried pressing the button to see if maybe he told me the procedure backwards an the button is actually to disengage.