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Looking at a M20K 231


ElCid05

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Good evening everyone. I have a question as I’m looking for my first Mooney and first airplane. I do know my insurance will be high and I’ve already received a couple quotes, but it’s in the budget. 
 

I’m looking at an M20K 231 with the GB engine. It does not have the Merlyn Automatic waste gate nor does it have an intercooler. 
 

I see differing information as to whether these are necessary. Is this plane one I should walk away from since it doesn’t have those items?

I welcome all the feedback and appreciate all the awesome information on this forum. 

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ElCid-

I am not an expert, but have been flying Mooney aircraft for 20+ years.  First aircraft, I'd steer clear of the 231.  Get a 201, an E or F model, all depending on your budget.  I think the 201's are overpriced in general, but a low time pilot can be trained to safely operate an E, F or J Model.  the 231 has a problem engine as far as I am concerned.  It's a whopping 10HP more than an E, F or J, so it's not all that much faster.  yes, it's a turbo - are you planning on regularly flying up above 12,000' MSL?  If so, could be a good plane for you.  Personally, if you're going the route of a 231, step up to a 252.

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Although the 252 is a superior plane, and I wish I had waited for one rather than buying a 231, the 231 is still a good plane, and if operated carefully, it will do the job. I don't fly very high every much, but the ability to easily get up to 14 to 17K, over most of the weather and a lot of the traffic is nice.

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Well, I have no direct experience with the GB. My aircraft has the LB plus intercooler and Merlyn wastegate. What I can tell you comes from watching the engine operate on a JPI 930. I don’t think the nonintercooled, fixed wastegate GB would be a very good choice. honestly. The GB had a reputation for running hot. With the fixed wastegate and no intercooler I think you would find it difficult to get much above 15,000. Its a combination of things. That is the critical altitude for the non Merlyn engine (maybe 15,500, but it varies depending on the day). The CA is much higher in my aircraft, about 22,500. I have been above it a few times, and the problem is that the climb rate becomes very anemic, probably 300 fpm or less. In addition, when you get up in the higher altitudes the thinner air does not cool anything very well. The Compressor Discharge Temp. redline on that engine is 280, and on most days you probably would hit that at around 17k. The engine would be struggling above the CA and probably overheating. I know the POH has book numbers up into the Flight Levels, but realistically I think you would find its not easy to get up that high with that combination. The LB with the intercooler and Merlyn wastegate is a much better option, The LB has inherently better cooling, the intercooler reduces the Induction Air Temperature about 100 dF, and the wastegate lets you get up quite a bit higher. If you don’t want to pay the cost for that combination, then the 201 might be about as good a choice as the GB engined 231. My .02.

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I am the proud owner of a 231. It is a wonderful airplane - but I would not buy one with a GB engine without the necessary upgrades.

Mine has the LB engine and the intercooler, waste gate, GAMI, etc. upgrades. It runs relatively cool, and has great climb performance. The turbo is definitely a plus. Still, even in this configuration, I would expect mid-time cylinder and turbo replacements, which mine had done before I bought it. What I don't particularly like is the fact, that takeoff is not with full throttle, which takes time to get used to.


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I bought  a stone stock 1980 231 with a GB in 1994 with 1077 hours.

like everyone else I followed the POH from Mooney and the engine only lasted just short of 1200 hours.

I had mine converted to a Rocket 305 and flew it another 1000 hours trouble free. LOVED that airplane.

‘At the time all the 231s were getting about 1200 hours. Any 231 without wastegate and intercooler needs one. Deduct the price of the upgrade from book. Also consider it a 1200 hour motor without them both. 
With both wastegate and intercooler And a good multi probe engine monitor they are great airplanes.

I bought a 1990 MSE (201) after having the 231/Rocket. I hated that airplane. Every time I flew it all I could think of is what it could not do.

It could barely struggle to 17000’ and could not maintain the MEA into Denver over Larks intersection.

sold it to a flat lander in Texas. 
 

I want another Rocket but could settle for a properly equipped 231 or 252.
 


 

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My first 231 had a GB engine with no UDC or Intercooler.  I don't recommend it.  It was a struggle on hot days to maintain even a moderate climb rate without significantly exceeding 400 F CHT.  As much as I tried to keep CHTs below 400 F, during the 3 years that I owned it I ended up having 3 cylinders develop cracks and 1 complete cylinder barrel separation, resulting in an off-airport landing.  The previous owner had the alarm value on the JPI set for 460 F, so who knows what CHT he was operating at.  

The 231 I am flying now has an LB engine with a Merlyn UDC, intercooler and GAMIs.  It is like flying a different airplane, and I can recommend it.  I too would prefer to have a 252 with the MB engine, but none were available when I was buying.

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Ever fly a plane in the flight levels?

The cool thing about a Mooney M20K...

It is as serious as GA flying gets...

If you only intend to fly it at 12k’...   The NA Mooneys are a bit more economically friendly for the lower levels...

Got your IR already?

Would love to recommend an M20K, and Transition Training that is proper for you... but you would have to discuss some of your background... and where you want to be...

Go Mooney!

Best regards,

-a-

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20 hours ago, RJBrown said:

I bought  a stone stock 1980 231 with a GB in 1994 with 1077 hours.

like everyone else I followed the POH from Mooney and the engine only lasted just short of 1200 hours.

I had mine converted to a Rocket 305 and flew it another 1000 hours trouble free. LOVED that airplane.

‘At the time all the 231s were getting about 1200 hours. Any 231 without wastegate and intercooler needs one. Deduct the price of the upgrade from book. Also consider it a 1200 hour motor without them both. 
With both wastegate and intercooler And a good multi probe engine monitor they are great airplanes.

I bought a 1990 MSE (201) after having the 231/Rocket. I hated that airplane. Every time I flew it all I could think of is what it could not do.

It could barely struggle to 17000’ and could not maintain the MEA into Denver over Larks intersection.

sold it to a flat lander in Texas. 
 

I want another Rocket but could settle for a properly equipped 231 or 252.
 


 

Another turbo convert. 
Once you have had a turbo, going backwards is really hard. 

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I recently purchased a M20K 231. It only has 400 hrs on the engine but so far I have no regrets. I use it strictly for a cross country plane up in the 16k to 17k altitudes. I live in KC MO and it is just a little over 4 hrs + or - to Daytona Beach for me. Still, no regrets.

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27 minutes ago, hubcap said:

I recently purchased a M20K 231. It only has 400 hrs on the engine but so far I have no regrets. I use it strictly for a cross country plane up in the 16k to 17k altitudes. I live in KC MO and it is just a little over 4 hrs + or - to Daytona Beach for me. Still, no regrets.

Another turbo convert!

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Knowing how a 231 has been operated is one of the critical pre buy elements as that’s a factor in engine longevity.  It could be luck, but the previous two owners who owned it since the overhaul were temperature hawks so I’m almost at TBO with great compressions and oil numbers. 
 

it would be hard for me to go back to a NA bird, I love having full power available when high.  
 

As others said, a 231 with the LB and intercooler are highly desirable for engine longevity.  
 

A 231 was my first Mooney but not my first airplane which was a Cherokee 180 which I put over 500 hours on.  It was a big jump with all the extra crap to manage but became pretty much second nature after about 20 hours or so.  
 

Get good transition training to get safe, then go fly a bunch in good Wx to get proficient, then some more to get comfortable before launching into tough weather/situations. 
 

 

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21 hours ago, carusoam said:

Ever fly a plane in the flight levels?

The cool thing about a Mooney M20K...

It is as serious as GA flying gets...

It is definitely different. Most of the time it is dead still, crystal clear over the top, and no traffic because the big iron is all higher and the NAs are all lower. But it has its own set of issues that take some getting used to.

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I have a 231 with a stock -LB + GAMIs and I really have none of the issues others have talked about. I typically fly between 10k’ and 13k’ (family doesn’t do canulas) at 35”/2550/11gph and see acceptable CHTs and good forward speed. Just make sure you have a solid engine monitor, which is true regardless of what K model or what features it has. 
 

That being said, I will be putting in an intercooler next time I have $8k burning a hole in my pocket. 

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Like most others (but maybe unlike many others) My plane originally came with a GB and fixed waste gate bolt and an intercooler. The CA was around 16k ft. I worked to keep the hottest jug under 380 degrees mostly running LOP. When I changed the engine out, it went to an LB with a Merlyn...now, my hottest jug runs around 320 degrees and the engine easily gets me into the flight levels. Bottom line, the GB needs to be switched out so budget accordingly...and for sure an intercooler must be attached...I do like the Merlyn as it greatly enhances my CA BUT it comes with as high or a higher workload...

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1 hour ago, Tom 4536 said:

My 231 has a GB-1, a Merlyn, an intercooler and a JPI 900. My hottest CHT is 330; hottest EGT is 1375. Oil runs 195 during climb and 180 at cruise.

Any benefits to my installing GAMIs? 

I have GAMI's...absolutely as they allow you to run LOP

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On 1/17/2021 at 5:48 PM, Mooney217RN said:

ElCid-

I am not an expert, but have been flying Mooney aircraft for 20+ years.  First aircraft, I'd steer clear of the 231.  Get a 201, an E or F model, all depending on your budget.  I think the 201's are overpriced in general, but a low time pilot can be trained to safely operate an E, F or J Model.  the 231 has a problem engine as far as I am concerned.  It's a whopping 10HP more than an E, F or J, so it's not all that much faster.  yes, it's a turbo - are you planning on regularly flying up above 12,000' MSL?  If so, could be a good plane for you.  Personally, if you're going the route of a 231, step up to a 252.

This is frustrating.  You're not an expert, but you make a blanket statement about "The 231 has a problem engine as far as I'm concerned."  Do you mean early 231s with the -GB engine?  If so, yes, there were early problems, which have been largely rectified with the -LB engines.  Add an intercooler and Merlyn and it's a fantastic plane.  A low time pilot can't be trained to safely operate one?  Jeez, tell that to the military, which routinely teaches low time pilots to fly jets.  

Sure, it only has 10 more horsepower than the J, and it isn't "...all that much faster."  But by that logic, your Ovation 3 has 100 more horsepower, and isn't that much faster than my 231...in fact, maybe a bit slower.  

Throughout the history of the 231, it has been discussed by armchair critics who've never actually flown them and just repeat what they've heard from early reviews of early model 231's.  Maybe get some updated information on the 231 before making broad statements.  Sorry for the rant...

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 Hello @ElCid05,  Owner of the "dreaded" 231 with the -GB engine here, although I cannot say mine is one of the dreaded examples. 1978hrs on the airframe and on the original -GB engine.  Flights in the mid teens are the norm.  No intercooler or wastegate or GAMI's.  Engine monitor?  Absolutely!  I fly LOP on every flight, 30", 2500rpm, 9.5-9.7gph all day long, hottest cylinder 365*(cyl#3).  I do think the 231s require an elevated work load to manage correctly but they are most certainly not a problem to handle.  I bought mine with 46.3 hrs in my log book with my PPL still dripping wet.  I found a good instructor (key) that knew the idiosyncrasies of the model and have never once regretted the purchase in the 5 years I've owned and maintained her. 

 

  If you do the due diligence before the purchase and you have the patience and instructor to learn the engine and airframe, I don't think you'll find a better bang for the buck with prices where they are on most 231s!  (my opinion)

 

Ron

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