I have a 3.7 with Alpha 1 Gen one. While running at cruising speed on plane suddenly lost all power to prop. No sign or sound of a prop strike. Small thump sound just before engine reved high obviously no longer driving the prop. but no loud banging, grinding or other noises. Engine starts and runs fine. Initial diagnosis was coupler. I did not run the engine long enough to worry about overheating while waiting for the tow. No rubber smell from the engine. Pulled the outdrive to check. Obviously can’t get to the coupler but it looks “ok” with just a light, but really can’t tell, no sign of stripped steel on the input shaft of the outdrive. Outdrive has oil, pressure tested good. When checking the outdrive the input shaft was difficult to turn but did get it turning by hand. No transfer of rotation to the vertical shaft and into prop. I pulled the cap off and it looks like the gears are completely gone. No teeth just a smooth round peice where the gears would sit in the horizontal shaft. Metal shavings and small peices of metal in the oil. Obviously needs a new upper unit( or whole unit), or rebuild. Question is…. Is it worth the “easier” repair first, prior to pulling the engine and checking the coupler. Is there any other reliable way to check the coupler without pulling the engine. I do have access to a garage with a gantry to do it, but now thinking it may never have been the couple, just similar symptoms, and would be a time saver. I have a lot of records from the PO but still don’t know the complete history. Besides potential maintenance neglect by previous owner(s) any other reason an outdrive would fail this way?
