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Sagging Engine, Worn Lords Mounts


GeorgePerry

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Since there doesn't seem to be one dedicated place that discusses M20S/M20R sagging engine problems (or droop) and information is scattered throughout the forum under different threads I thought I'd summarize my experience with the problem and how I got it fixed.

 

Started 5 months ago when I had the pre purchase inspection performed by a MSC in TX.  After getting a clean bill of health, (or so I thought - see separate thread) I arrived to pick up my new to me Eagle.  It was a very low time aircraft with only 470TT.  The first thing I noticed was a 1/2 inch gap between  the top of the spinner and the cowl.  With dismay and some sarcasm I asked the A&P if he thought this was normal (a rhetorical question).  He said, engine sag is a common problem, the mounts were inspected and were in "good" shape.  I was upset at having just paid for an annual/prebuy and this is the first thing I noticed from 20 feet away.  

 

After some back and forth negotiations I closed on the plane and flew home knowing that I had some airplane maintenance to do in the near future.  I returned to my home field and asked my local shop to also inspect the mounts as the aesthetics of the sag really bugged me.  They too said, common problem with Mooneys.  I still wasn't satisfied and started doing some internet research along with looking through dozens of threads on MS.  I did find that earlier short and mid body Mooneys have a shim procedure designed to help fix the problem but there is no such "official" procedure for IO550 equipped aircraft.  After several PM's with another mooneyspace member and eagle owner, I also learned of a service bulletin that applies to M20R's but not to eagles.  However several eagle owners have run into the same problem.  Basically insulation behind the upper mounts doesn't allow for proper torque to be set on the bolts and can cause sag.      

 

After an air to air photo flight where I had some very high resolution pictures taken, the sagging engine looked even more pronounced airborne than it does on the ground.  I had heard a few A&P's say that sagging engines will "align themselves" in flight.  Based on my experience, that is clearly not the case.  After seeing these pictures I knew I couldn't put off fixing the problem any longer.

 

The next step was to take the plane to a highly regarded MSC in PA.  Weber Mooney inspected the mounts and were able to determine in short order the engine shock mounts were very well worn, had excessive play and recommended that they be replaced.  I wasn't surprised since the mounts had been on the plane since new (16 years) and the sag was so pronounced. Additionally they showed me how much movement my engine had compared to an M20R that had new mounts.  There was a big difference and even though there as still ample clearance between the spinner and cowl, it solidified the fact it was time to replace.  

 

The good news is that Weber MSC had a set of the very hard to find lords mounts (PN Lords 1 x J9613-75 and 3 x J9613-76) on hand.  Also as they got into the job they noticed that one of the front spacers had been improperly installed.  This made the sag even more pronounced.  Weber was able to swap the mounts and install the spacers correctly in less than a day.  Now the engine is properly aligned with the cowl.  They also checked my plane and found that I did not have any insulation behind my engine mounts and the torque on my mounts was correct.  The SB didn't apply but the piece of mind was worth them checking.

 

The total cost for all for mounts was just under $1500 and their labor rate was very reasonable.  I am very please to have my sagging engine fixed and found a knowledgable shop that does great work at a fair price.  

 

The attachments show pictures of the sag both on the ground and airborne, along with the Part #'s out of the M20S / M20R parts catalog and page 1 of a 6 page service bulletin.   Once I have a good weather day, I'll post the before and after pictures.   

 

Since posting I've received a couple of questions from M20R owners asking if the Lords engine mount part numbers are the same.  the answer is yes.  M20S and M20R use the exact same lords mounts.

post-6885-0-45614100-1419386113_thumb.jp

post-6885-0-23325200-1419386117_thumb.jp

post-6885-0-33854800-1419386121_thumb.jp

post-6885-0-60933000-1419386128_thumb.jp

post-6885-0-29681700-1419386133_thumb.jp

post-6885-0-67249900-1419387088_thumb.jp

post-6885-0-89899500-1423101072_thumb.pn

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Since there doesn't seem to be one dedicated place that discusses M20S/M20R sagging engine problems (or droop) and information is scattered throughout the forum under different threads I thought I'd summarize my experience with the problem and how I got it fixed.

 

Started 5 months ago when I had the pre purchase inspection performed by a MSC in TX.  After getting a clean bill of health, (or so I thought - see separate thread) I arrived to pick up my new to me Eagle.  It was a very low time aircraft with only 470TT.  The first thing I noticed was a 1/2 inch gap between  the top of the spinner and the cowl.  With dismay and some sarcasm I asked the A&P if he thought this was normal (a rhetorical question).  He said, engine sag is a common problem, the mounts were inspected and were in "good" shape.  I was upset at having just paid for an annual/prebuy and this is the first thing I noticed from 20 feet away.  

 

After some back and forth negotiations I closed on the plane and flew home knowing that I had some airplane maintenance to do in the near future.  I returned to my home field and asked my local shop to also inspect the mounts as the aesthetics of the sag really bugged me.  They too said, common problem with Mooneys.  I still wasn't satisfied and started doing some internet research along with looking through dozens of threads on MS.  I did find that earlier short and mid body Mooneys have a shim procedure designed to help fix the problem but there is no such "official" procedure for IO550 equipped aircraft.  After several PM's with another mooneyspace member and eagle owner, I also learned of a service bulletin that applies to M20R's but not to eagles.  However several eagle owners have run into the same problem.  Basically insulation behind the upper mounts doesn't allow for proper torque to be set on the bolts and can cause sag.      

 

After an air to air photo flight where I had some very high resolution pictures taken, the sagging engine looked even more pronounced airborne than it does on the ground.  I had heard a few A&P's say that sagging engines will "align themselves" in flight.  Based on my experience, that is clearly not the case.  After seeing these pictures I knew I couldn't put off fixing the problem any longer.

 

The next step was to take the plane to a highly regarded MSC in PA.  Weber Mooney inspected the mounts and were able to determine in short order the engine shock mounts were very well worn, had excessive play and recommended that they be replaced.  I wasn't surprised since the mounts had been on the plane since new (16 years) and the sag was so pronounced. Additionally they showed me how much movement my engine had compared to an M20R that had new mounts.  There was a big difference and even though there as still ample clearance between the spinner and cowl, it solidified the fact it was time to replace.  

 

The good news is that Weber MSC had a set of the very hard to find lords mounts (PN Lords 1 x J9613-75 and 3 x J9613-76) on hand.  Also as they got into the job they noticed that one of the front spacers had been improperly installed.  This made the sag even more pronounced.  Weber was able to swap the mounts and install the spacers correctly in less than a day.  Now the engine is properly aligned with the cowl.  They also checked my plane and found that I did not have any insulation behind my engine mounts and the torque on my mounts was correct.  The SB didn't apply but the piece of mind was worth them checking.

 

The total cost for all for mounts was just under $1500 and their labor rate was very reasonable.  I am very please to have my sagging engine fixed and found a knowledgable shop that does great work at a fair price.  

 

The attachments show pictures of the sag both on the ground and airborne, along with the Part #'s out of the M20S / M20R parts catalog and page 1 of a 6 page service bulletin.   Once I have a good weather day, I'll post the before and after pictures.   

As long as you've gone to all of that effort to fix that problem, now might also be the perfect time to also check the dynamic balance of your aircraft propeller. 

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Russ

 

Great question.  It was unscientific but convincing.  They grabbed the prop and lifted the engine up and down to see how much play (movement) the current mounts allowed.  It was at least a couple of inches up and down.  Then compared that amount of movement to an aircraft that had new mounts.  They knew mine were worn but did this for my benefit and the difference was dramatic.  They also removed the cowl and visually inspected the mounts for obvious signs of extreme wear or improper installation, cracks spacers missing etc.  It was obvious to me that the guys at Weber were experienced and knowledgeable, unlike the shop that performed my prebuy.  The A&P's at my local shop are very capable "generalists" but not Mooney experts.  The guys at weber are experts who obviously know Mooneys.  

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  • 3 weeks later...

The cowl on the eagle is the same as the ovation but the prop is a "one off" and the spinner might be a different size….Thus the 1/4 in space.  I du-no??  When I get the screaming eagle mod completed, it comes with a new prop and spinner.  I'll be interesting to see if it's the same or different.  Oh-well close enough and the gap is uniform, not perfect, but uniform.  I suppose it'll do. 

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George,

I'm guessing that spinners must come in 1/2" sizes.

The next one up is too large, so they went with 1/2" too small...?

I didn't notice the gap until I was inspecting the new one after getting installed...

It's an interesting question for the Hartzell people when you go through the Screemin' process.

Best regards,

-a-

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  • 3 weeks later...
  • 3 years later...
On 12/24/2014 at 7:29 AM, GeorgePerry said:

Russ

 

Great question.  It was unscientific but convincing.  They grabbed the prop and lifted the engine up and down to see how much play (movement) the current mounts allowed.  It was at least a couple of inches up and down.  Then compared that amount of movement to an aircraft that had new mounts.  They knew mine were worn but did this for my benefit and the difference was dramatic.  They also removed the cowl and visually inspected the mounts for obvious signs of extreme wear or improper installation, cracks spacers missing etc.  It was obvious to me that the guys at Weber were experienced and knowledgeable, unlike the shop that performed my prebuy.  The A&P's at my local shop are very capable "generalists" but not Mooney experts.  The guys at weber are experts who obviously know Mooneys.  

Don't mean to bring up an old thread but it is a very good and useful post.  Just wondering if the new mounts helped reduce any vibrations or otherwise helped make for a smoother flight?  I'm planning to check my mounts soon since they appear to be originals - though not much sagging, there is a bit of play.  My mechanic mentioned sag is common but usually don't want to change unless a mount is actually "bad".  Guessing he'll be doing the same test you mention above.  If the engine also ran smoother after the change, would be a no brainer for me since I do seem to get a bit of vibration compared to other IO-550s I've flown.

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Methods people use to reduce engine vibrations...

1) Dynamic prop balance...

2) Gami balanced fuel injectors...

3) new engine mounts...

4) Get a look at the new Ultra engine mounts... the engine moves 2X the normal engine mount allowance... as shown in a video by the Mooney Sales guy...

PP thoughts only...

Best regards,

-a-

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1 hour ago, Chris K said:

Don't mean to bring up an old thread but it is a very good and useful post.  Just wondering if the new mounts helped reduce any vibrations or otherwise helped make for a smoother flight?  I'm planning to check my mounts soon since they appear to be originals - though not much sagging, there is a bit of play.  My mechanic mentioned sag is common but usually don't want to change unless a mount is actually "bad".  Guessing he'll be doing the same test you mention above.  If the engine also ran smoother after the change, would be a no brainer for me since I do seem to get a bit of vibration compared to other IO-550s I've flown.

Chris,  my prop had a close fit at the bottom of the spinner where you couldn’t insert your index finger.  A few years ago I had Maxwell replace the mounts.  Still sagged. Since then I put on an MT prop with spinner and the cowling.  MT spinner has plenty of clearance.  We should be able to lift the engine a bit by pushing up on the spinner and prop but not a lot.  The video Anthony describes where Lee of Premier shakes the engine up and down is very spongy looking.  Does your compass vibrate up and down a lot?  

Russ

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That's how my ovation is.  It sits a little low on the ground.  When I did the overhaul we replaced the mounts and triple checked that the washers are all in the right place.  Its the same.  I do have a hartzell three blade prop and not the original mccauley.  I have no idea if that's part of the reason.  There is some play if you push on the prop but nothing like Lee's video.

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28 minutes ago, hypertech said:

That's how my ovation is.  It sits a little low on the ground.  When I did the overhaul we replaced the mounts and triple checked that the washers are all in the right place.  Its the same.  I do have a hartzell three blade prop and not the original mccauley.  I have no idea if that's part of the reason.  There is some play if you push on the prop but nothing like Lee's video.

Mine as well, although I have the original McCauley three blade. I replaced the mounts two years ago and it was fine for a while. Now the sag is back.  

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16 hours ago, carusoam said:

Methods people use to reduce engine vibrations...

1) Dynamic prop balance...

2) Gami balanced fuel injectors...

3) new engine mounts...

4) Get a look at the new Ultra engine mounts... the engine moves 2X the normal engine mount allowance... as shown in a video by the Mooney Sales guy...

PP thoughts only...

Best regards,

-a-

Thanks - I have GAMIs and prop is relatively new which is why I'm looking at the mounts.

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14 minutes ago, Chris K said:

Thanks - I have GAMIs and prop is relatively new which is why I'm looking at the mounts.

New doesn't imply it was actually balanced or balanced well, check the log books for the install and see if they actually dynamically balanced it.

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14 hours ago, Txbyker said:

Chris,  my prop had a close fit at the bottom of the spinner where you couldn’t insert your index finger.  A few years ago I had Maxwell replace the mounts.  Still sagged. Since then I put on an MT prop with spinner and the cowling.  MT spinner has plenty of clearance.  We should be able to lift the engine a bit by pushing up on the spinner and prop but not a lot.  The video Anthony describes where Lee of Premier shakes the engine up and down is very spongy looking.  Does your compass vibrate up and down a lot?  

Russ

My engine does not move as much as the demo video for the new airplanes, probably different style mounts.  My compass is fine in flight.

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7 minutes ago, Steve W said:

New doesn't imply it was actually balanced or balanced well, check the log books for the install and see if they actually dynamically balanced it.

Good point to double check, though seems ridiculous that whomever mounted would have skipped that step.  Would my regular mechanic be able to perform this or must it be removed and sent to a prop shop?

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Just now, Chris K said:

Good point to double check, though seems ridiculous that whomever mounted would have skipped that step.  Would my regular mechanic be able to perform this or must it be removed and sent to a prop shop?

A  dynamic balance is done on the plane as it's as really about the prop and the engine working as a system, much like how tires get balanced once they're actually put on rims rather than in isolation. Here's an AOPA article on the process:

https://www.aopa.org/news-and-media/all-news/2018/january/22/propeller-maintenance-balancing

 

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