I was working on basic take-offs and taxiing with a client ( a new I.A. in town ) on the lake. It was light rain (45F) and a little mist off in the distance.
Almost every time we got the C-172 off the water the engine would start to loose RPM when we were over the causeway road at
the end of the lake. Right during a pull up.
Carb heat application cleared it up every time. Using carb heat during half the take-off run reduced the
problem by about 80%. With just a little drop in rpm for a few seconds.
I suspect that water is being thrown up into the intake during high power plow or even step taxi and it happens to turn into ice by the time we were over the other end of the lake. After flying around for a minute or two with some carb heat usage, the problem goes away all together. Although if we flew around in a high power climb we eventually managed to pick up carb ice in flight today due to the high moisture situation.
The air flow in the cowling might be goofed up by the super large hole around the new smaller exhaust pipe. ( PHOTO) at certain angles of attack it might be let cold damp air directly blast the carb itself. Or maybe it just goofs up the proper air-flow and allows water to inter the engine compartment.
One thought from another pilot as that I have a cab float out of adjustment. He thinks the aplication of carb heat is reducing teh rpm enough that the carb can then keep up with demand. The seaplane prop does indeed let me crank up the rpm...
Talk about annoying.... and dangerous.