Engine losing power
Today I was flying to a fly in at Natchez Mississippi. Flying my Aircam. I was flying at 5000 RPMs. After one and a half hours of flying, the right engine began to lose power. The RPMs drop down to around 3500. There was an ag strip below me so I landed. Did the mag check. everything OK. Other than let the engine sit for 10 minutes, I didn't do anything else. Upon restart, the engine would maintain 4000 RPMs. But no more. I took off with both engines at 4000 RPMs and flew to the next airport. After the plane sat for approximately three hours, I attempted to run the right engine again. It would not go over 3500 RPMs. There was a mechanic on the field. He removed the bottom spark plugs on three of the cylinders just to see what they look like. They were clean. I Then crank the engine. At that point I had full throttle up to 5200 RPMs. I took off and flew for two hours at 5000 RPMs on both engines with no further problems.
The same thing happened 2 weeks ago on a local flight but alter landing it cleared up. I had full throttle.
The only other thing going on with the engine is about a month ago, my coolant level was down a half inch. In four years of flying, I have never had to add any coolant. The plastic overflow bottle was still half full. The reservoir on top of the engine was a little low.
After the mishap today, I noticed that the plastic overflow bottle was almost full. The reservoir on top was a little low.
When the problem shows up, I can advance the throttle smoothly to 3500 or 4000 RPMs. After that, it starts getting mushy are bogging down.
Any ideas on what to look at?
