I can only comment on the 912UL engine and I’ve been very impressed with it.
My first one was replaced at 5500 hours. In that time we never had a problem with it.
All we did was service the aircraft as per the manual. All of which was done by myself apart from the gearbox overhaul.
It did have the starter replaced and the carbs were overhauled which showed dirt to be the cause of rough running at full power.
I then replaced with a new engine at 1/3 of the price of a new O-200 and after 600 hours is running just as reliably as its predecessor.
We did the gearbox at 600 hours and it was inepect, repair or overhaul as necessary. As dictated by the chap who did the work.
In fact the only reason we pulled the engine was we were told the gearbox wouldn’t overhaul again and I couldn’t see any point in buying a new gearbox to put on such a high time engine.
On stripping the only part of the engine to show wear was the camshaft.
I have a manifold pressure guage for a twin sitting in front of me now. It’s a weighty thing and would not be something you would want to add to the empty weight of a ULM.
Obviously the electronic equivalent would be less weighty, but it was regardless just an idea. I think if you were flying a 912 it would be nice to have real time info on carb synch. Checking it otherwise is a time consuming procedure. It’s not like a twin carb motorcycle where you can check it after a ride occasionally (before shutdown) with synch gauges hanging on the garage wall for that purpose.
You can synch the carbs with a balance tube in place – there is no flow down that tube when the throttles are in synch. The reason you very often do it by pulling the balance tube is because that’s the easiest way to access nipples to connect the gauges. That does not preclude having permanent MP connections made elsewhere and using them to synch the carbs while the balance tube is in place.
Twenty years ago I thought I might like a Tecnam and with maybe 20 more years to fly I occasionally think about what I’d do if FAA medical qualification became problematic and I wanted to stop getting medicals and fly an LSA eligible plane. Rotax engines weigh into that thinking but for me any aircraft powered by them would be costly to own in comparison to keeping my low hassle O-320 (that makes 50% more power) running beyond its current 52 years since assembly. If I do need to overhaul it sometime after I retire, it’ll be about $15K and I’ll do it myself. Simple works for me.
