The International Cessna 170 Association

Hi guys,
Is there an STC required to change motors from a C-145-H2 to an O-300B? What type of approval or paperwork would be required?

The 170 Association has a STC for that swap.

Thanks Karl. I was looking through the members section for that information but didn't see it. Can someone point me to the details?

Thanks Gary!

nippaero wrote:Hi guys,
Is there an STC required to change motors from a C-145-H2 to an O-300B? What type of approval or paperwork would be required?

You ask if an STC (or some other bases of approval) is needed to swap a C-145-2H for a 0-300-B which is for all intent the exact same engine. Continental in the '55-'56 time frame decided as all their competitors where marketing their engines named by cubic inches rather than horse power, that they need to do the same. So the C-145-2 became the 0-300-A and the C-145-2H became the 0-300-B.

And the answer today is yes. And the reason is that today we take everything we read literally and we can not apply common sense. Of course in order to apply common sense one would have to have experience and know when it could be applied and we have much less of that today in the FAA than ever before.

The problem is the TCDS for the Cessna 170 lists C-145-2H but does not list 0-300-B. So an 0-300-B is not a legal engine by the TCDS alone. Never mind there is some evidence Cessna delivered 170s built in the '55 time frame with 0-300-B model engines installed.

Cessna never had the 0-300-B added to the TCDS for the 170 though they did for the 172. Also, if you have a '48, the C-145-2H was never approved for that model though there is no reason it shouldn't be.

But do not fear should you have a 0-300-B in any model. The Association does indeed have an STC that covers the 0-300-B in any model and we sell it today very reasonably at $75 for members.

Regarding the O-300 STC, did we ever sort out the Spinner issue?

Was there an issue?

I never saw an issue.

Bruce Fenstermacher wrote:

nippaero wrote:Hi guys,
Is there an STC required to change motors from a C-145-H2 to an O-300B? What type of approval or paperwork would be required?

You ask if an STC (or some other bases of approval) is needed to swap a C-145-2H for a 0-300-B which is for all intent the exact same engine. Continental in the '55-'56 time frame decided as all their competitors where marketing their engines named by cubic inches rather than horse power, that they need to do the same. So the C-145-2 became the 0-300-A and the C-145-2H became the 0-300-B.

And the answer today is yes. And the reason is that today we take everything we read literally and we can not apply common sense. Of course in order to apply common sense one would have to have experience and know when it could be applied and we have much less of that today in the FAA than ever before.

The problem is the TCDS for the Cessna 170 lists C-145-2H but does not list 0-300-B. So an 0-300-B is not a legal engine by the TCDS alone. Never mind there is some evidence Cessna delivered 170s built in the '55 time frame with 0-300-B model engines installed.

Cessna never had the 0-300-B added to the TCDS for the 170 though they did for the 172. Also, if you have a '48, the C-145-2H was never approved for that model though there is no reason it shouldn't be.

But do not fear should you have a 0-300-B in any model. The Association does indeed have an STC that covers the 0-300-B in any model and we sell it today very reasonably at $75 for members.

It's interesting that while the O-300B with the valve on the front left of the case is approved for the C-172, the two-position McCauley or the Koppers Aeromatic propellers which require this valve are not on the TCDS. My guess is that Cessna had extra O-300B engines in stock and mounted them on these 172's with the valve wired closed. Cessna must have used up their stock of O-300B engines by the time they rolled out the C-172A because the TCDS for this plane only lists the O-300C and O-300D as approved engines.

TCM continued to offer the C145-2H/O300-B engines after the propellers were no longer available because of the possibility of aircraft already equipped might still need those engines.

The C145-2H and the O300-B engines are the same engine with only a nomenclature change. Since the props were no longer available there was no reason to approve them for installation.

I’m not following you George. Why is the O-300-B on the C-172 TCDS when there is no propeller that uses the hydraulic valve (or in the case of the Koppers Aeromatic, the valve port) listed on the C-172 TCDS?

Because that engine is ELIGIBLE for the those props.... but it isn’t REQUIRED to use those props. It quite permissible to use the other props listed for the airplane as well.