There is a good deal on interest in the 150 HP modification of the Cessna 150.  There is also a good deal of misinformation and misunderstanding about the airplanes.  It seems that many folks that have never set foot in a hot rod 150 have a great deal of knowledge about the way they fly, handle and how awfully expensive they are to operate.

I do not claim to be an expert but I do have the experience of going through the modification process and flying one for a few hundred hours.  The following is my best effort to provide an objective look at the concept and the fact of a great little airplane, the Cessna 150, with a 50% power increase.  I do admit that I have some difficulty in being totally objective even though I no longer one a 150/150.  The fact is I love the little fellows.




The installing a Lycoming 0-320 engine to replace the stock Continental 0-200 engine is a moderately popular conversion for Cessna 150 airplanes. 


As in all engineering designs there compromises must be made.  When compared to a stock 150 the 150/150 has significantly enhanced performance numbers but at the cost of additional weight and fuel burn.


As would be expected the addition of an additional 50 horse power to a 100 horsepower airplane produces some significant changes in performance.  The most notable performance change is in climb.  The stock 150 is not known for its’ ability to climb.  A 50% power increase completely changes the picture.  The 150/150 will climb like the proverbial homesick angle.  The increase in cruise performance while substantial is not nearly as spectacular as the improvement in climb performance.


After all is said and done a 150/150 is sill a Cessna 150, with muscles.  The weight and balance restrictions and the V speeds are the same.  No a 150/150 does not stall at a higher speed, it still has a gross certified weight of 1600 pounds.


Why Would Anyone Want a 150 HP Cessna 150?


There are probably more reasons for having a 150/150 than there are 150/150s.  Just a few reasons that come to mind are:


A 150/150 makes a fine banner tow plane. 

A 150/150 can be used to tow gliders. 

A 150/150 is an excellent patrol aircraft.  It is as fast or faster than a 172, lower operating cost and is more maneuverable. 

 A 150/150 is a great plane for getting in and out of short strips.

 A 150/150 is a hot rod.  Not real fast on the big end but quick to get started.

 A 150/150 is much like a sports car, nimble, quick on the controls with good performance.

 A 150/150 is a good choice for high elevation airport operations.

 A 150/150 is just plane fun. (pun intended)


If you think that you might like to have a 150/150 but are not sure get a demo ride.


How Does a 150/150 Perform?


The thing that a 150/150 does best is CLIMB.  The table below gives the climb performance of my airplane equipped with a Sensenich 74”X53” climb prop.  The data was obtained by conducting three timed climbs to the airplane’s service ceiling.  The data from each climb test were averaged and the results were linearized using the least square fit method.


DENSITY ALTITUDE                       IN FEET


DENSITY ALTITUDE                       IN FEET























The prop makes a huge difference in the climb performance.  When the same series of flight test were performed using a 56” pitch prop the climb rates were 25% less than those with the 53” pitch prop.


Cruise performance is important to all of us.  If we wanted to go slow we would get a Cub.  The table below gives the cruise performance data at 75% power for my plane, equipped with a “climb prop”.  It is interesting to note that there was little loss in cruise speed at low altitude and a slight increase in cruise speed at altitudes above 9000’ when the prop was re-pitched from 56” to 53”.  This is most likely due to the fact that the engine will turn faster at higher altitudes and allow more power to be developed.


The cruise data is the result of averaging the results of three timed five mile speed runs.



DENSITY ALTITUDE                       IN FEET



DENSITY ALTITUDE                       IN FEET
























How Can One Get a 150/150?

 Purchasing a 150/150

There are two legal ways to get a 150/150, build one or buy one.

 At any given time there are a handful of converted 150s advertised for sale.  The asking price for 150/150s runs from a low of $18,000 to a high of over $50,000.  There are currently 150/150 listed for sale on the Cessna 150-152 Club web site and in Trade-A-Plane.  When purchasing a 150/150 the same attention to the condition of the airplane as with any other purchase is necessary.  In addition to the normal items to look for like engine condition, corrosion, paint, interior, etc. it is highly desirable to obtain ALL of the paper work pertaining to the conversion, including the STC drawings.


 When you purchase a 150/150 you get a certified, flying airplane that you can fly right now and upgrade, if required, on your time and fiscal schedule.

The other way to obtain a 150/150 is to do the modification yourself.  This will entail at a minimum buying an airframe, an engine, a prop, a spinner, the STC, the installation kit, and numerous bits and pieces, then locating a shop that is capable and willing to install the conversion.  Next comes the waiting and added expenses while the shop makes the installation and finds all sorts of little things what will need to be resolved, all taking time and costing money.


 There will also be additional items that you will most likely like to add at the time of the conversion.  Since the 0-320 is thirstier than an 0-200 long range tanks while not an absolute necessity are a convenient item if you plan to use the plane for cross country travel.

 There are a couple of companies that hold STCs for the 150 HP conversion.  Or at least there were two a few months ago.  Aircraft Conversions Technologies and Robert and Barbara Williams, DBA as Avcon or Bush, both hold conversion STC.  More about them later.

 Obtaining the engine is not an easy task.  The STC calls for a Lycoming 0-320-E2D.  While these engines are by no means rare you can’t get one at the 7-11 store.  The prices and conditions will vary greatly and one will have to be very careful in order to obtain a good value in a used engine.  Of course you can always go with a new engine. $$$ Ouch!

 Then comes the prop and spinner.  A used prop will be very difficult to locate and a new one will most likely be required.  Again $$$ Ouch!  The spinner will be available from the 150 HP conversion STC holder but most likely will not come with the kit.


When you get all of the big chunks gathered up you can load it all in your little red wagon and haul it out to your conversion shop.  The STC holders will give you an estimate of around 90 to 100 hours to make the conversion.  In my experience unless the shop that you are using is well experienced in making the conversion these numbers are way low.  For your budget add 50% to 100% to the STC holder’s estimated labor cost.

 When the conversion is completed carefully monitor the paper work and be sure that there are 337s for all of the major items.


 Where Can I Get The Conversion Kits?

 There are three sources for STCs and conversion kits. 


Aero Upgrade LLC

8252 Cessna Drive Medowlake Airport

P O Box 25272

Colorado Springs, CO  80936

Phone 800-833-8322

Fax     800-833-8622




2121 Wildcat Way

Porterville, CA  93257


Talk to Harry Dellicker 


Barbara and Bob Williams

Bush Conversions (Avcon Conversion)

P O Box 431

Udall, KS  67146

Phone:  620-782-3851

Fax:      620-782-3853


The Williams are very nice people and provide quality product with good documentation and are very helpful.  They are however a little slow to respond.  The last quote on delivery that I got from them was six weeks.  I honestly can not recommend their company because of chronically slow service.


How About Auxiliary Fuel Tanks?


For a plane that is going to be used for cross country travel long range or auxiliary fuel tanks are a very nice option.  Running the 0-320 at 75% power will consume 8.4 gallons per hour.  With stock fuel tanks you have 22.5 gallons of usable fuel.  That translates to about 2:40 to dry tanks.  If you land with a VFR legal thirty minutes of fuel remaining you will have an effective range of around 275 miles in no wind conditions.   


At Clinton there was a lot of interest in and questions about my 150/150 and 150 HP conversions in general.  Since I have returned home I have had a number of email inquiries about the conversion. The following is an attempt to answer as many of those questions as possible. I hope that Jeff and some of the other 150/150 drivers will chime in and flesh out the points that I miss of correct me where I am wrong.


It should be noted that I have only accumulated around 60 hours of flying in my little airplane since I started flying it in March. I have learned a lot but I still have a lot to learn. Steve can tell you that I still can't spot land it worth a hoot, I smacked the

fantail of the mythical A/C carrier at Clinton.


For me one of the most important issues when considering an engine conversion is will the resulting airplane fit my needs. I want an airplane that will allow me to make cross country trips of 200 to 500 miles without the need to RON. Where I live it is necessary to fly high to avoid getting beat up by turbulence in the spring and summer.   My home airport is 2800 MSL and our second home airport is at 6800 MSL. I need to be able to take off at gross weight when the DA is above 9000'.


Most important of all since I have retired I need an airplane that will perform all of these task at a relatively low capital cost and with a low operating cost. For the last 25 years I have been flying complex airplanes with big bore engines. The $3000 insurance bills

and $4000 annual inspections/maintenance have priced those birds put of my nest.


My decision to get into a 150/150 came after a couple of years of study and consideration.


A stock 150 just does not have the power plant to meet my needs.


A 172 was my first choice but it has very anemic performance at high altitude. I own half of a Cherokee 140/150 with my son but again it does not climb well or perform well at high altitude. (I flew a Cherokee for over 1500 hours and an well acquainted with it's

capabilities and shortcomings.) The 180 HP 177 is a little better performer than the 172 and Cherokee but not a lot.


A 182 performs well at altitude but the capital cost and operating cost are just too high for my budget.


While the 150 is small in most aspects it has essentially the same  wing as the 172. When the same engine is installed on a plane with 600 to 800 pounds of weight you get a plane that will CLIMB!


With insurance for a 150 at $500 per year and annual inspection cost at $500 per year. The 150/150 started to look good. Now add the fact that the 0-320 has a 2000 hr TOB and that a good overhaul can be had for $10,000 as opposed to the 1200 hr TBO and $25,000 overhaul cost for a TSIO-520 and it looks even better. On my normal trip of

200 nm the 150/150 burns 14 gallons of fuel as opposed to 22 gallons and the picture becomes clear. Sure the trip will take an extra 25 minutes but that is a small price to pay for the economic benefits.  What would I rather do with those 25 minutes than fly?


The decision was made. The 150/150 fit my mission profile to a tee and it is a plane that I can afford to own and fly. I decided to do the conversion rather than buy a converted airplane. I was really planning on a 180 HP 0-360 conversion. After I purchased my 1973L I found what seemed like a very good deal on a 1968 H 150/150 so I bought it too. We later found that the H model had BAD corrosion in the right wing and the decision was made to jack up the STC and drive the L model under it. I lovingly call the result my Sport Hawk.


In addition to adding the 150 HP engine there were a number of other mods added. Each of these items was installed to fill a specific requirement.


The most often asked question is "How do you like your 150/150". The answer to that question is easy, I love it. It performs pretty much as I expected. It will get off of the runway at 9000' DA in a reasonable distance and climb out at around 700 FPM.


With the current prop (that is a whole 'nother story) the Sport Hawk at rated gross weight will climb from 3,500' to 17,000' DA in 26 minutes. While not a blinding rate of climb it will get me up in to the cool, smooth air in a reasonable time.


Cruise speeds at 75% power run from 120 MPH TAS at 1500 feet to 137 MPH TAS at 12,500 feet density altitude. At 75% power the 0-320 burns 8.4 GPH (source Lycoming). Dropping the power to 65% reduces the fuel flow rate to 7.3 GPH and will reduce the cruise speed by around 5 MPH.


 Pulling the black knob back to 50% drops the fuel flow to 6 GPH and farther reduces the cruise speed by another 5 MPH. Note: 50% power for the 0-320 is equal to 75% power for the 0-200.


The next most often question is "How much did it cost". I am not yet prepared to tell ANYONE what the total package cost; I don't even want to know myself.  I will say that if you really want or need a 150/150 you will be a LOT better off, both economically and time wise, to sell your current plane and buy a flying converted 150/150.


There is a lot of interest in the Flint auxiliary fuel tanks.. To safely and conveniently fly the trips that are normal for me more than 22.5 gallons of fuel is needed. The Flint tanks, that add an additional 23 gallons of useful fuel and 35 pounds of empty weight.  They are installed in the outboard portion of the wing. The last rib has a hole cut into it and the tank slides into the wing. A fuel pump is installed between each aux tank and main tank and when needed fuel is pumped down from the aux to the main. I fly until I have burned 12 gallons of fuel, then pump fuel from the aux tanks until the fuel gages on the main tanks read full. When I have burned 24 gallons I pump the fuel remaining in the aux tanks into the mains.


The Flint tanks are well made, the documentation is excellent and the support is outstanding. However, the resulting fuel system is much more complicated that is commensurate with a 150. If they can be found the stock Cessna long range tanks (patroller tanks) even at only 40 gallons are a simpler and better choice.


DelAir holds an STC on converting standard tanks from 22.5 to 40 gallons.   I really feel that this is a better solution.  The installed cost of the long range tanks are about the same as the auxiliary tanks but maintain the simplicity of the original Cessna 150 fuel system.


To assist in fuel management I installed a JPI FS450 fuel flow computer.  I have flown with a fuel flow computer for many years and given the inaccuracy of stock fuel gages it gives me a good deal of comfort to have a cross check on my fuel burn. I have found the readings of the flow computer agree within +/- 0.5 gallons with the fuel truck meter.


Since there is no manual information on power settings for the prop, engine, airframe configuration I use the flow meter as my primary means of adjusting power. The Lycoming owner manual provides a set of curves for fuel flow at various power settings. 75% = 8.4GPH 65% = 7.3 GPH 55% = 6.2 GPH I don't pay much attention to the Tachometer,  I just let it run what it takes to get the specified fuel flow. As I climb the tach reading heads on up toward the red line. Talking to Jeff and Chris I find that I burn more fuel than they do and that is due to the fact that they don't flog their engines as hard as I do.


I installed a four point Alcor EGT to assist in accurate leaning. I don't feel that the cost and complexity of a four cylinder engine analyzer is justified for the low compression, normally aspirated 0-320. I lean to 50 rich of peak for best economy, per the recommendations in the Lycoming owner's manual.   I found that the "lean until the engine runs rough the enrich the mixture a bit works just a well as the EGT.  If you just have to have another gage in the panel make it a four place CHT; if you take care of your cylinders they will take care of you.


I installed a King KFC200, two Icom A200 com units,  a Narco 122 nav radio (VOR/ILS),  a Sigtronics two place intercom and rounded it out with a S-Tec Model 40 coupled auto pilot.  I kept the Narco AT 150 transponder that was in the plane. My primary navigation chores are accomplished using a Garmin CPSMap 295 GPS. I had the radio system and static system tested and certified for IFR flight for those occasions that it may be necessary to go IFR for safety.


It has long been my personal policy not to fly single pilot IFR without at least a minimal auto pilot. The S-Tech Model 40 coupled to the VOR and a DG with heading bug serves nicely to assist in maintaining heading during long trips or in IFR conditions.  It is also a big help on long trips.



All in all I am very pleased with the package that I call the Sport Hawk. My trip to and from Clinton last week was my first really long cross country trip in the plane and I very pleased with the results. With favorable winds a 1000 mile trip is easily accomplished in a day, it took me 7:30 and one fuel stop to fly the 943 miles to Clinton. When the winds are against me I think that 700 miles would be more comfortable, the return trip took 9:30 with two fuel stops and I was pretty tired when I got home.


Would I recommend a 150/150. I surely would. The performance is pretty spectacular and it is the most fun I have had flying in a long time. However, if you are flying in low country and don't require strong climb and high altitude performance a stock 150/152 is just dandy and a lot cheaper.


As with most things in life the 150/150 entails some compromises. For strong climb and a little increase in speed you must pay with flying a heavier airplane; forget 1600 pounds and be prepared to take off and fly most of the time at above certified gross weight. You also pay in increased fuel consumption. Sure you can pull back to 50% power and burn about the same rate as a stock 150 but I'll bet that you won't.


Would I build another 150/150? No way. You can buy a flying airplane for a LOT less than you will have tied up in converting your own plane. It took nearly eight months and a bunch of buck to get the Sport Hawk flying.


I hope that the foregoing answers questions that you may have about 150/150 conversions. Please bear in mind that these are my opinions and you may get a completely different slant from some other 150/150 owner.