Lycoming O-235 C1

Mar 15, 2019
Looking for comments/experience/opinion on the O-235 C1. I unfortunately have no experience with this engine, but have heard both good and bad. Are there any standout reasons not to buy a 7ECA with one?

Bob Turner

Well-known member
Apr 4, 2018
You might be thinking of the obsolete and unsupported O-290. I think the O-235 is about like the little Continentals - bulletproof and easy to overhaul.


Well-known member
Apr 3, 2018
Tacoma, WA
The good: 2400 hour TBO, the longest life piston in the business.
The bad: It's not 150hp.

I wonder if the Sparrowhawk STC for 125hp is available for the Citabria application.


Staff member
Mar 27, 2018
New Jersey, USA
My '68 has the O235-C1 and it's awesome. About 5.5 gph, easy to start cold or hot with 2 or 3 shots of prime, at 2500 RPM the airspeed indicator is usually just under 110 mph. In the summer with me, a friend, and fuel we're still climbing out at 500 fpm, below 1000 msl at most of the airports around here.

Run it often and don't baby it and they're known to go to TBO.
Feb 20, 2020
Our family had a PA-12 with a 100 hp Lycoming O-235-C engine. On the PA-12 type certificate, the O-235-C is rated for 100 hp at 2600 rpm continuous using 73 minimum octane fuel, while the O-235-C1 is listed as an alternate engine and is rated at 115 hp at 2800 rpm for takeoff, and 108 hp continuous at 2600 rpm using 80 minimum octane fuel. Both have a TBO that was increased a few decades ago from 2000 hours to 2400 hours, provided they still had all Lycoming parts and they commonly go all the way to TBO.

The O-235-C and O-235-C1 engines use the same mags, carburetor and prop flange and have the same specifications. The difference is that the O-235-C1 has a provision for a two position propeller control valve, while the O-235-C does not. (The PA-12 type certificate has several very interesting two position propeller options listed - it was apparently a big thing in 1946-47.

Short version, we ran our O-235-C at 2800 for takeoff and propped it accordingly with a Sensenich metal prop while operating it on 80/87 and 100 LL. It was a bulletproof engine that never had a significant maintenance issue during the 937 flight hours our family owned it.


How does this apply to a 7ECA thread? Both the O-235-C and O-235-C-1 engines are listed on the 7ECA type certificate.

The O-235-C2C is listed on the type certificate for the 7ECA as an alternate engine. It's still in production but is rated by Lycoming at 108 hp continuous at 2600 rpm, or alternatively at 100 hp at 2400 rpm. However on the 7ECA type certificate it is listed as 115 hp at 2800 rpm along with the O-235-C1 I think the major difference from the O-235-C1 is in the propeller flange, but don't quote me on that. The McCauley 1C90ALM72 or McCauley 1C90CLM72 are specified for the above engines,

The O-235-K2C is another alternate engine on the type certificate and it is rated at 115 hp at 2700 rpm. The type certificate lists is at 118 hp at 2800 rpm for takeoff, and at 115 hp and 2700 rpm continuous. Again, I think it has a Type 1 propeller flange. The type certificate specifies the Sensenich 72CKS8-0 for the 7ECA with a Lycoming O-235-K2C


The Continental O-200-A used in the first year or so of 7ECA production was rated for 100 hp at 2750 rpm using 80/87 fuel. Most of the complaints I've heard about the O-200-A engines in general is that they usually don't actually develop 100 hp on takeoff or climb due to RPM limits and a cam shaft design that gives it max power at RPMs it rarely sees. Continental even admits that under optimum conditions it only dynos at 97 HP.

Consequently, many pilots regard the O-200-A as performing more like a 90 hp or even 85 hp engine than a 100 hp engine on takeoff. In comparison the C-90 is rated at 95 HP for takeoff and initial climb and delivers more torque at low rpm due to the cam shaft design. The C-85-12 will deliver 97 HP maximum, so many pilots regard the O-200-A as having less, or at best no better, performance than the C-90 or a C-85-12.

There's a 100 hp O-200-A powered Champ on the local field and it doesn't climb any faster or cruise any faster than an 85 hp Champ. What it gained in horsepower was offset by the increase in weight. An O-200-A powered 7ECA falls in the same category and isn't regarded as having the same take off climb performance as the O-235 powered 7ECA. The McCauley 1A100ACM69 is specified for the O-200-A with a static r.p.m. at maximum permissible throttle setting between 2600 and 2400 rpm.


As an aside, the O-200 made a comeback with the LSA category in the form of the O-200-D, which is still being produced. Continental increased the compression from to 8.5 to 1 (up from 7 to 1), so they are an honest 100 hp engine now. They also have lighter accessories including lighter oil sump, starter, alternator, and magnetos, as well as hollow crank shaft and cam shaft, a lighter prop flange, and tapered cylinder fins, to get the weight down to 199 pounds. However, that's a lot of metal to take out of the engine, and it remains to be seen if it'll hold up in service as well as the O-200-A, which was quite reliable. The O-200-D has a 2000 hour TBO with an extension to 2200 hours for flight schools or operators that keep them in regular use.