I broke an input shaft on my 14-71 about 3-4 years ago. Motor would start, run, show 6-7 lbs boost, you could wing it as much as you wanted out of the water(no load). When loaded, it would pull to only about 2400 rpm, (not quite on plane), backfire and quit. It would start right up after that though. Added fuel pressure gauge where I could see it, replaced carbs with borrowed units, checked the blow-off valve, replaced the entire ignition, plugs, wires, dist, hotwired the ign directly to the battery, tried a small fuel cell of known new fuel, with a different electric pump, and it was the input shaft..... It was broken at enough of an angle that it would turn the rotors without much load, but when the boost was higher than 6-7 lbs, it would distort the front gear cover enough to slip for a few revolutions, just enough to kill the motor. The motor could windmill it, with help of the broken shaft, to 5500 rpm with no load, but under load there wasn't enough air to run it. Craig from BDS claims to only have heard of that twice in 40 years. Check your shaft and gears, by hand everything felt fine on mine, no extra slack or anything. We finally put a block of 2x4 between the rotors and could slip the shaft with a 1/2" drive ratchet fairly easily. New shaft, and no issues. I still have both parts of the old shaft. Good luck. TIMINATOR
