Recently I was beginning my takeoff roll and instead of getting close to 2700 rpm I only got about 2500 then as I briefly continue the t/o roll it dropped a little further to about 2350. My MP appeared to increase about 2" during this process until I aborted. The second attempt had similar results.

I shut the plane down and called my a/p and discussed it with him. He really didn't have an answer. I restarted and again did a full runup and cycled the prop etc and all appeared normal again. This time everything appeared fairly normal. RPM was at 2650, perhaps 50 below normal, and MP was where it should be, and I have not been able to reproduce the problem again.

Looking for ideas on how to proceed. I assume their could be tach issues, but it did appear that MP was a little high making me wonder if that was it. And since I can't get it to duplicate I am stumped.

Thanks for any thoughts!

Clarence

At the beginning of the takeoff roll, I was making full power. A second or so later both MP and RPM decreased so I aborted the takeoff. Performed another run-up, same results.

Turns out the coupling boot that connects the air filter/cowling to the carburetor had a couple of fasteners come loose. The boot was folding in on itself as the air in the cowling became pressurized from ram air and was reducing the amount of air the carburetor could take in.

You have your mechanic give it a look if you are carbureted.