New Mooney pilot: M20K 231 vs 252

[Jay Aranha]

Hi everyone, just joined, currently shopping for my first Mooney, and am looking at the M20K.

• Did not find a consolidated discussion on this topic via the search, so kicking one off.

A few questions to start:

• I see the 231 has to be flown more carefully given it lack many of the 252 upgrades. What are the most important unique considerations relative to a 252?
• What are the must have upgrades on a 231? What are nice to have extras?
• Is the speed difference between the two noticeable? What is the bigest driver to making the 252 faster given similar HP?
• Any recurring ADs to watch for on either/both aircraft?
• What are the biggest problem areas to ask about beyond fuel tank re-seal, Turbo/Cylinders/CHT management?

Thanks!

Jay

 

Edited August 25, 2022 by Jay Aranha

[Pinecone]

Having just purchased a 252......

The 252 has an intercooler and an automatic waste gate.  So on takeoff, you push the throttle forward and check the manifold pressure to make sure nothing screwy is going on.  In the 231, as I understand it, you push up the power, keeping an eye on the manifold pressure, stop before the limit, let the turbo catch up, then fine tune.  During climb, you do nothing to the power settings in the 252, versus tweaking the manifold pressure in the 231.

In cruise, as I understand it, in the 231, as you change fuel flow or RPM, you have to fine tune the manifold pressure.

IMO, the 252 is what the 231 should have been.

You can add an intercooler and auto waste gate to a 231.

The 252s also have 24 volt systems and speed brakes are standard.  Every one I looked at had oxygen, but not sure if it was standard.

Some of the speed comes from better performance in the flight levels.  252 has a max ceiling for 28,000, and a critical altitude (max altitude for full rated power) of 24,000 feet.

The neat thing is, the 252 can be converted to Encore specs.  You convert the engine from -MB to -SB.  All external, prop governor and waste gate.  New manifold pressure gauge and tach markings.  Lower gear legs, doors, dual puck brakes, master cylinders and the control surface weights.  This gains you 230 pound increase in max gross weight.  My 252 has been converted and has an 1119 pound useful load.  So even with the Monroy long range tank STC, I can fill the tanks, put in two people and still carry a full baggage area.

Flying mine home, I was at 13,000 feet, showing 173 KTAS on 13.5 GPH running rich of peak.

Now for the bad news.  They only made 231 of the 252s.  And since they are so great (personal opinion  ), they seem to show up for sale less often and at higher prices.

[Fly Boomer]

51 minutes ago, Pinecone said:

IMO, the 252 is what the 231 should have been

All true.  I would only add that many or most 231s have had enough aftermarket pieces added to be close to a 252.

[Ethan]

One huge benefit to a 252 is the second alternator - a real weak link in the Mooney 231. One big drawback of the 252 is a lesser useful load from an already paltry one on the 231. 
 

I have finally gotten my useful load over 1000 pounds but it took a vacuumectomy and removing the old Century 31 autopilot and replacing it with the new Garmin autopilot. Would love another 200 pounds though.

[Fly Boomer]

6 minutes ago, Ethan said:

Would love another 200 pounds though

Beechcraft.

[Ethan]

Or Cessna. Or Piper.

[Will.iam]

3 hours ago, Pinecone said:

 

IMO, the 252 is what the 231 should have been.

You can add an intercooler and auto waste gate to a 231.

While you can add a merlin wastegate controller, to call it automatic is misleading as one assumes it’s automatically controlling the MP like the 252 but it really only stabling the manifold pressure you set with the throttle which helps with bootstrapping and because merlin can completely close the gate unlike when it was fixed from the factory it allows a higher service ceiling than factory. I. E. You are still responsible for overboosting so no firewalling the throttle on takeoff and any pressure changes like changing altitude will require you to readjust the throttle. Where as a 252 will hold the MP you set no matter climbing or descending and is far easier on the pilot.   
 

check out this linked thread of a new mooney owner that made this very assumption between the 231 and 252. 

 

[DonMuncy]

I agree with everything the others have said. I have a 231 and wish it was a 252. However, the 231 is a good plane and it soon becomes second nature to keep up with the MP adjustments.

[Pinecone]

5 hours ago, Ethan said:

One huge benefit to a 252 is the second alternator - a real weak link in the Mooney 231. One big drawback of the 252 is a lesser useful load from an already paltry one on the 231. 
 

I have finally gotten my useful load over 1000 pounds but it took a vacuumectomy and removing the old Century 31 autopilot and replacing it with the new Garmin autopilot. Would love another 200 pounds though.

 

Encore upgrade.  230 pounds more.

[carusoam]

Find @CharlesHuddleston’s plane for comparison….
 

Charlie just listed his plane for sale around here yesterday…

Many upgrades…

He is trading for a much larger plane…. Business must be doing well!  
 

The hard part of buying a nice M20K…. Finding them… and being ready to pull the trigger…

PP thoughts only, not a plane sales guy….

Best regards,

-a-

[Pinecone]

Yes, if you are looking for a 252, get your financing approved and get in touch and set up an escrow account for the deposit and purchase.  

I got mine because I was ready to close NOW.  From listing to closing was less than 2 weeks, over a 3 day holiday weekend.

I used Dorr Aviation to do the financing and Aero-Space Reports for escrow and title.

[Red Leader]

You must consider the price difference. A nice 252 will be many tens-of-thousands of dollars more than a comparable 231. On my most recent trip, I was cruising between 11,500 and 13,500 at about 29" MP averaging about 11.5gph LOP at 165kts. With a 903lb useful load, my 231 is a good travelling machine. I also have the Merlyn and Intercooler, so my performance is not far off the 252. What was said earlier is true, most 231's have upgrade mods to improve their performance (like mine) so the minor difference in cruise speed and the greater attention to instruments may not be enough to justify the additional expense of a newer version (read 252). If you have plenty of disposable income, this is a decision that can be difficult to make - consulting other pilots on this platform is the right way to start. If cost is an issue, consider a 231 that already has the upgrades performed. The speed of our Mooneys is why we all love them some much! Of course, the new interior makes mine go much faster!

[hubcap]

I own a M20K 231. The 252 does have a few amenities that the 231 lacks, but I couldn't be happier with my 231. The 252 does make engine management easier, but as @DonMuncy points out, engine management becomes quite a non-issue with proper training and flying. 

I would be cautious about buying a 231 that doesn't have a good engine monitoring system. The TSIO-360-GB engine was original equipment in the 231 but later models have the TSIO-360-LB engine, which is considered to be superior due to engineering improvements. I have the JPI-900 which makes it very easy to manage the engine without over-boosting, and to keep CHT's at appropriate temperatures. I added the Turboplus intercooler and Black Magic pressure controller to my 231 after I purchased it.

My POH calls for 40" of Manifold Pressure when taking off, but I was trained to use 36" as max, before adding the intercooler. I never run 40" of manifold pressure.

My useful load is 950 lbs but will go up in the fall a bit  after we upgrade the panel. With full fuel, my wife and I can take bring 120 lbs of baggage with a 6-hour range and IFR reserves.

Travelling we typically fly in the  mid-teens or lower flight levels and cruise at 160-165kts LOP or 175-180kts ROP. 

LOP = ~10 gal/hr 

ROP = ~12 gal/hr

I would guess that there is about a $50k premium for a 252 over a 231, but I am sure that other's here have a better idea of the delta. If you can find a great 252 for a price that you can afford - GREAT!! If not, I wouldn't hesitate to buy a 231 in good shape.

[Browncbr1]

if you find a 231 with an intercooler, such as turboplus as mentioned above, just save the ~$100k premium of a 252 and just go for the intercooler 231... 

There is actually one for sale in the classified forum that is near here in east TN.

Edited August 27, 2022 by Browncbr1

[Fly Boomer]

On 8/25/2022 at 11:03 AM, Ethan said:

One huge benefit to a 252 is the second alternator

If the OP is still following this topic, I would caution that not all 252s have the second alternator — it was an option.  I ran into this when I was looking.

[Will.iam]

5 minutes ago, Fly Boomer said:

If the OP is still following this topic, I would caution that not all 252s have the second alternator — it was an option.  I ran into this when I was looking.

Excellent point and adding a second alternator is not a simple easy process nor did the single alternator fair well with the battery. Seemed i read where there were issues experienced with single alternator 252 that the dual alternator 252 never experienced. I tried to buy two 231’s that where sold before i could get my finances in line then missed a 252 that was already under contract after it had posted only 2 days earlier! So when the 252 i finally got posted, the same day i called and said i wanted it would fly out the next day to do an inspection. We took 4 days going over everything and waiting for funds to clear so that on the 5 day it was mine but while that was going on he had 6 other people call in those days with one in europe that would come out if my financing fell through. I just got lucky it was a 252 is all. 

[Fly Boomer]

2 hours ago, Will.iam said:

I just got lucky it was a 252 is all

I only quoted your last sentence, but your entire post is on the mark.  I looked at dozens of airplanes online, flew to 4 of them for a better look, and finally bought the fifth.  This took many months.  But the fact is, you have to know precisely what you want, what you will settle for, and what you can pay.  Also, I will second what you said about having the money in escrow so you can electronically sign documents, and move the money in minutes — not days or hours.

[Will.iam]

8 hours ago, Fly Boomer said:

I only quoted your last sentence, but your entire post is on the mark.  I looked at dozens of airplanes online, flew to 4 of them for a better look, and finally bought the fifth.  This took many months.  But the fact is, you have to know precisely what you want, what you will settle for, and what you can pay.  Also, I will second what you said about having the money in escrow so you can electronically sign documents, and move the money in minutes — not days or hours.

I find it almost comical when someone new comes on here saying a laundry list of things they have to have in their plane not realizing that what you want and what is available to be purchased is vastly different and they soon discover they have to lower their requirements or be prepared to wait for a very long time and accept the possibility it may never show up. It’s not unicorn shopping but Ferrari shopping comes to mind (exotic rare fast hand built)

[M20F]

1 hour ago, Will.iam said:

I find it almost comical when someone new comes on here saying a laundry list of things they have to have in their plane not realizing that what you want and what is available to be purchased is vastly different and they soon discover they have to lower their requirements or be prepared to wait for a very long time and accept the possibility it may never show up. It’s not unicorn shopping but Ferrari shopping comes to mind (exotic rare fast hand built)

This is very correct.  When I started looking it was Bonanza, Comanche, and then Mooney.  I would have really liked to have had the Bonanza but just couldn’t find the right one.  In the end I got a Mooney and very happy with it all these years later.  
 
The other thing is folks get wrapped up into what the Jones’s have rather than their own mission.  A lot of people drop out of GA because they simply feel it is too expensive or a hassle but often that is because they bought a plane so far from their mission.  If you are a weekend hamburger person a high performance turbo airplane is not for you.  
 
Thanks for talking about the elephant in the room.  

[HawkGT]

Another option to consider is a M20K 231 that was converted to a 261 or 262 with a -MB engine by Mod Works or Mod Squad.  You get all the benefits of the 252 engine which includes an improved intake runners, intercooler and wastegate but the price is closer to a 231.  As stated before, it may also have the second alternator but not all do.  There seem to be plenty of these around so they pop up routinely in the market. This is the path I chose in my search for a M20K and very happy with my selection.  I’ll also point out that built in O2 was an option for the 231s and many of the planes I considered had it installed. I would love the brakes and useful load increase of an Encore but just couldn’t justify the cost.

[Will.iam]

One of mine that got away was a 231 with the FWF 252 conversion. It was lighter thus had more useful load than my 252 but covid had shut down the boarders and i could not go up to Canada to get it. Then the taxes DER to convert it back to N ferry permit, for the states became cost prohibitive. I did see where someone bought it and put in alot of new avionics and was selling for $90k more than what it was when i looked at it.  Didn’t last long the 2nd time either.