|Maule Operators Blog
|I bought my first Maule in 1995. It was an 1970 M-4 220 with original Razorback cover and mid time engine. I
decided I would recover it with the Poly Fiber process and have it ready to go the next spring. Two and a half
years later I finally got it in the air! First bit of advice. Don't buy a project because you think you will save
money or with the idea of making money when you sell it. Do a project if you enjoy working on airplanes. If you
want to fly. Pay a bit more, find a good sound airframe and engine, put gas in it and go flying.
So far I've owned the M-4 220, an M-5 235 that I modified to an M-6, and an MX7 160. All started out as projects.
All took longer than I thought they would to complete. In the process I've gained some experience about used
Maules and what to look for when buying. I've seen a lot of people buy a cheep airplane only to find out in a
couple of years they can't afford to maintain it in good airworthy condition. So they lose interest and sell the
airplane. Second bit of advice. It takes money to own and maintain an airplane. Be prepared for unexpected
expenses and know they are part of owning an airplane.
This seems to happen most often with engine related issues. Most of the problems can be traced back to the
engine setting around for years at a time with low usage. I'd rather buy an engine that had 1500 hours on it in the
last 5 years than one that is 20 years old and only has 500 hrs. total time. When I bought the MX7-160 it had 300
hrs since overhaul, 50 hrs since tear down and inspection for prop strike, but had set 2 years without flying. We
did a annual inspection. It had great compression, low oil consumption and ran great for 80 hours. Then I started
noticing higher oil use. To make a long story short I ended up tearing the engine down, replacing the cam and
lifters, polishing the crank and honing the cylinders. The lifter faces were starting to deteriorate and little flakes of
metal were floating around in the oil grinding away on all the other engine surfaces. I had changed the oil and cut
the filter open three times and never found a thing to worry about. I'm sure if I had run it another 50 hours I would
have needed a major over haul. Low engine usage equals rust equals problems.
COST OF OPERATION
Nov. 2010 I now have put another 100 hrs on the MX7-160. The engine has been running great. We are
working on replacing other maintenance items such as a worn throttle cable. Over all this 160 hr. stripped down
"Sportplane" should be an economical airplane to operate. I have been quite surprised with the performance. The
airplane is 250lbs. lighter than my M6. Therefore the stall speed is less so I can land slower and shorter. I have
the standard climb prop so I only cruise at 105 kts, but on climb out with me and 40 gals of fuel, 4000ft DA I get a
climb of +1000 ft/min. Take off with 180lb. pilot, 25 gals of fuel, DA 3500 ft, no wind = 300 ft ground roll.
Nov. 2011 One year and 300 hours later. I guess I shouldn't have used economical and airplane in the same
sentence. I started setting aside $25.00 per hour for maintenance needs of the MX7-160.. I later went to $35.00
and now $40.00 per hour plus $10.00 per hour engine reserve. Over the year I added extended tanks which is
an upgrade not routine maintenance but you still need to set aside money for such items. I did have to replace a
cylinder because the valve guide came lose in the head, Why? I don't know. ( 750 hrs. on a new Millenium ) Most
every thing else was general wear and tear.
Dec. 2012 Just finished another 100hr./ annual. Nothing major to report. I did upgrade the ELT to a 406 type.
Other expenses over the year included - Fine wire spark plugs ($49.50 ea), new mags and harness ($1900.00),
replaced the front floor boards, installed the new type of tank vents. I have flown N10240 a little over 200 hours
this past 12 months. Setting aside $40.00/hr. I have about $400.00 surplus for the 2012 calender year and
$800.00 in the checkbook since we started setting money aside. I have also set aside $10.00/ hour for engine
The one expense I now see I haven't planed for is a recover/paint job. At the present a good quality job will be in
the $20,000.00 to 25,000.00 range. If you don't care about looks you can expect the modern covers to test good
for 30 years or more but the structure underneath may need work before that. Most of us don't keep an airplane
for 30 years. The recover cost is should be taken into account at the purchase of the aircraft. This is one cost
that can be devastating to aircraft ownership if you aren't prepared for it.
Jan. 2013 This being tax preparation time I decided to look at the operation expenses of my M6. I had airframe
and engine overhauled in 2005. So now I have 7 years and 1800 hours on the airplane. During that time some of
the major expenses - prop overhaul ( I run part 135), replaced 5 cylinders (it was a cheep overhaul and used
rebuilt and welded cylinders), new mags and harness and new exhaust system. So all that plus annuals, oil
changes and regular maintenance - $26.69 per hour. Now of course that doesn't include buying 31" Bushwheels,
auto fuel STC and wing mod, etc. All those I consider optional not true operating expenses but should be factored
in to your calculations. Since I run part 135 I will need to replace the engine at 2000 hours. I have looked into
what a factory reman with new hoses, ducting, engine mounts,etc and installation would cost. Looks to be in the
$35000.00 range which means $17.50 / hour. Now yes with a good core I can get by for less but I'd rather plan for
the high for the worst case.
May 2013 Not again! I had to make a precautionary landing in my MX7-160 when I was out on a pipeline patrol.
Luckily I was over the flat farm land of central Montana and taxied up to a farmstead. I had no compression on
one cylinder. After removing it I found the valve guide had come loose in the head and had broken into pieces.
The same thing had happened in Nov. 2011. (See above) This was a different cylinder. (1000 hr. SMOH) I
started to see a pattern here. When I got the airplane back to Cut Bank we pulled the other two cylinders. With a
small hammer and punch we could tap out the other valve guides! We sent all four cylinders in to ECI. After they
inspected them they didn't say there was a problem, but they sold us new cylinders for $300.00 ea. We split the
case again to clean out the debris in the oil sump and replace bearings. Things are now back together and
running fine. We'll see how things go from here. That's now twice I've had to tear the engine down because of
problems beyond my control. What will be next?
Mar 2015 I have now installed my overhauled O-540 in my M6. The base price for the work was a little under
$26000.00. Since this was not the first overhaul on this engine I needed to replace some gears in the accessory
case. That was close to $5000.00 for serviceable replacements. After the added expenses of removing
,shipping,reinstalling, new baffles, engine mounts, new ducting,etc. the price is around $33500.00.
Jan. 2016 I have been putting $20.00 an hour aside for regular maintenance in the 160hp Maule. I haven't had
any other major engine problems since installing the new cylinders. After I pay for an annual the check book will
be back close to $0. At that amount it leaves nothing for up grades in avionics or airframe upgrades. I'm going to
start setting $30.00 per hour aside for maintenance.
AUTO FUEL STC
Oct. 2011 I have just now completed installing the STC from Maule flight. If you can get fuel with out ethanol it
might be something to consider. Premium auto gas is running $1.25 to a $1.50 a gallon less here at this time. I
hope to pay for the expense in a year's time. The process involves removing the Dukes boost pump and installing
an electric Facet pump that runs continuously and another pump as a boost pump. Then you cut holes in the
cowling to duct outside cool air to the gascolater and engine driven fuel pump. All to prevent vapor lock.
For some reason I am having the problem of dry carbon fouling of the plugs when using auto fuel. This happens
only on the 160HP engine not the 235HP. I'm running the mixture as lean as I can all of the time but still get
fouling. You can take an air hose and blow most of it off. It's like a graphite powder on the plugs. I have called
both Peterson and Maule and they say they have never seen this problem. I have been running 38E plugs going
to the hotter 40E has helped some. One thing that does seem to help is running a 25% Avgas blend. It seems to
clear the carbon off of the plugs. I'm going to try a 10% blend and see how that works.
1/26/2012 I have been running a 10% to 15% avgas blend and fine wire plugs. Everything is working great. At
the last oil change I checked the plugs and there was no carbon fouling.
Dec. 2013 Over the last year I have been using the 10 -15% blend and things have worked great. I have been
saving $1.25 to $1.50 per gallon. The bad news is my distributor won't be able to get ethanol free premium after
the first of the year.
Dec. 2014 I have found another source for ethanol free fuel. I have used it now for about 800 hours in the
MX7-160 and 600 hours in the M6-235.
Jan. 2016 The auto fuel STC is the best money I have spent on airplane maintenance. It's not for everyone. It will
take 300+ hours to pay for it's self. So it will depend on how much you fly your airplane and if you can get ethanol
6/15/12 I have been pleasantly surprised on the way the 160HP performs. I gave some instruction in a
C172-180hp. The MX7- 160 will get off the ground quicker, climb faster, and land shorter than the Cessna. The
172 may be a little faster in cruise. Click to see some short field take off and landings in the MX7-160.
5/22/16 I have been using a Hartzell 81" prop for the last six years. Since I instruct in other Maules I have
noticed the Hartzell is lacking in performance when compared to the McCauley 81" and 80" three blade props. In
my research I ended up contacting Flight Resource about MT propellers. In short I was able to obtain a Field
Approval for an 83" MT prop. It does have better take off thrust and climb performance and is smooth running.
That being said it would have been lots cheaper and logical to have overhauled my Hartzell and I could have lived
with the slightly less performance. But in airplane ownership logic is seldom a major factor. If you have a project
and no prop or had damaged a prop beyond repair I would certainly consider an MT.
As time goes on I will add to this rambling narrative.