MaxwellSmart86

Finally a small update… found one bad plug - figured we were on to something. But still a vibration. Compressions are all good, plugs are all tested/good. Both magnetos checked. Magneto timing checked. Prop was dynamically balanced 2 months ago. We dug through log books and we found the Lord motor mounts are 32years old. They don’t have tons of hours but 32 years is a long time if the logs are right. Motor is not sagging, mounts look ok visually and are squishy still. Bottom mounts maybe look a smidge sagged. We decided to do motor mounts. It’s good maintenance no matter what. I’m curious what we learn, I will continue to post. I spoke to a 30-year vibration expert, he told me any mounts beyond 10-15 years can easily equate to doubling the vibration. He went through all details with me and agreed mounts are next on the list. I’ll continue to post as we learn more…

I think I might have made progress last night. Took the plane out for 2hours, tried all different settings, 25-square on the ground holding the brakes, WOT with 2200, 2300, 2400, 2500 at low altitude, same thing at high altitude. All settings seem to have this vibration I feel present - some worse than others. Finally at WOT/2,500rpm/7,500ft we noticed the Left mag had much more of a rumble to it then the Right mag. On the right mag, you could continue to fly the plane and you almost couldn’t tell you were on one mag. On the left mag, there were noticeable hiccups and those hiccups had the same vibration/shake feeling as what I’ve been feeling in the yoke. Also, I only have a digital EGT but when I’d run the right mag my EGT would increase from 1325-1425 in a matter of 15 seconds. On the left mag, the EGT would go from 1325-1375 but also get there very slowly. I'm thinking I have a left mag (plug, wire, whatever) not firing clean. I will call my A&P tomorrow and relay all of this. i think I might be close to answer. Thank you all for the advise and suggestions.

Thank you, this is all adding up to me digging more into the vibration I have. Based on everyone’s feedback, it’s not just a 3-blade prop versus 2-blade prop and it likely is not “normal” - I suspect something else. I hope my A&P can peak soon so I can report back.

Thank you all for the feedback so far, this is all a helpful place to start. I believe I'm finding that even with a 3-blade prop on an M20C, I likely should not have significant vibrations... I called my A&P today as well, we are going to start digging together along with all the comments above (and any further comments here). Thanks much!

What would you like pictures of? if you fly a C, what do you feel for vibration at cruise speeds? Thanks!

I am a new user to MooneySpace but I have been referencing MooneySpace for the past 6-months while I pursued purchasing my first plane. I now am a proud owner of a very well kept 1965 Mooney M20C. I am hoping to get some feedback from all of you since this is my first Mooney (I flew Cherokees, Archers, Cessnas, etc. in the past). I have McCauley 3-Blade Scimitar prop with 200hours on it since new and about 800hours on the current engine. Here's my question - What do all you M20C owners see for vibrations while you are cruising in your C? The reason I ask is that when I cruise at 7,500ft, WOT and 2,500rpm - I feel a noticeable vibration in the yoke and panel (you can visually see the yoke vibrating a bit). Not terrible like the wings are coming apart, but noticeable enough to almost be uncomfortable. If I back off to 2,400rpm/WOT it is less and at 2,400rpm reminds me of flying our Cherokee 180 - a slight vibration in the yoke and panel (sort of the hum of the engine). The problem is that the plane is so new to me, I don't know what is "normal". I had the prop dynamically balanced last week to .065 IPS but that made zero difference in the vibration at 2,500rpm. I am going to have my A&P check some of the basics under the cowl to make sure we don't have something obvious touching/rubbing. In the meantime, what do all you C owners experience? Thanks so much! I love my new plane, just running down all these little loose ends.