I have a 1993 200 hp Johnson on a 23' Proline that has about 400 hours on it. Over the weekend it developed two problems. Problem 1 occured after trolling for a couple hours at around 1100 rpm. When running in at full throttle (around 5000 rpm), engine lost speed (from say 40 to 35) for maybe 20 seconds and then back up to full. This happened a couple of times over the weekend after this as well. Problem 2 occured at the end of the trip. When running back to port on about a 15 mile run, a knocking sound was apparent only when running around 3500-4000 rpm. Running fullout it was fine although I did encounter problem 1 once during the run. The trip entailed about 25 hours of running time of which 23 hours was trolling. I had the VRO disconnected on this engine last year and mix oil at 50-1. Until this point the engine has had no problems. Engine was tuned up and lower unit lube replaced with synthetic last August. Any thoughts on next steps? I thought about doing a decarb and maybe running some carb cleaner through.
