O-300

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cmathis

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CMathis
My club is considering purchasing a '67 Cessna 172 with the O-300 engine. I have read and heard they are prone to lead fouling and to be certain to properly lean on the ground and in the air. What other gremlins do these engines have? Do they usually make the recommended TBO if properly managed? Any reason why you wouldn't want to fly behind one?
 
cmathis said:
My club is considering purchasing a '67 Cessna 172 with the O-300 engine. I have read and heard they are prone to lead fouling and to be certain to properly lean on the ground and in the air. What other gremlins do these engines have? Do they usually make the recommended TBO if properly managed? Any reason why you wouldn't want to fly behind one?
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I have exactly one hour behind one of those in an older 172. I seem to remember it being pretty smooth like most other 6 cylinder continentals, but other than that I'm not sure of any gremlins it has. The lead fouling you mentioned is a common problem in most other low powered continentals and if it's like others, I'd imagine carb ice potential could be an issue too.
 
It's an O-200 with two more cylinders. Lead fouling not a big issue, carb ice slightly more prevalent than Lycomings. The only other consideration is that for 145 HP you have those extra two cylinders to deal with maintenance-wise and at overhaul time.
 
Sweet smooth running little engine. Only problem with is that it just ain't quite big enuf' for a 4 place airplane.
 
I had one couple years. I initially used tcp additive in it, but as it had a auto gas stc, I started using that. It loved it and was very cheap to fly. I have a newer 172m and I don't think it's any more powerful and useful load is much worse. Kinda wish I wouldn't have sold it.
 
Thanks for the input thus far. Seems the only complaints are possibly some lead fouling and carb ice potential. I keep hearing how smooth they are so I am interested to go do the test flight and see for myself!!
 
Theboys said:
I had one couple years. I initially used tcp additive in it, but as it had a auto gas stc, I started using that. It loved it and was very cheap to fly. I have a newer 172m and I don't think it's any more powerful and useful load is much worse. Kinda wish I wouldn't have sold it.
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Yeah the useful load on this one is right at 900lbs!
 
cmathis said:
My club is considering purchasing a '67 Cessna 172 with the O-300 engine. I have read and heard they are prone to lead fouling and to be certain to properly lean on the ground and in the air. What other gremlins do these engines have? Do they usually make the recommended TBO if properly managed? Any reason why you wouldn't want to fly behind one?
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Carb ice is about it, yes they are good engines, a little less horsepower than the 320 is all.
 
Silvaire said:
The only other consideration is that for 145 HP you have those extra two cylinders to deal with maintenance-wise and at overhaul time.
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This. Only major downside is that they are more expensive to overhaul than the typical 4-bangers in comparable 4 seaters. And cranks can be a biotch to find these days.
 
What do they add, $1hr? :dunno: When you add camshaft issues with the Lycoming into the equation I bet average cost of overhaul difference is a rounding error crapshoot either side in the scheme of ownership.

I'd be interested to see if Crower or someone could do a reasonable priced, one off, billet steel crank. As an owner produced part it shouldn't be difficult to get it accepted with Crower's data.
 
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I have a '63 172 with an O-300. After about 2,000 hours behind that engine, I'll repeat what everyone else says. Smooth but not overly powerful.

A very reliable engine.
 
Smooth running,not enough power to fill the seats,no maint problems that I experienced. Had a 62 172.nice airplane engine combo.
 
cmathis said:
My club is considering purchasing a '67 Cessna 172 with the O-300 engine. I have read and heard they are prone to lead fouling and to be certain to properly lean on the ground and in the air. What other gremlins do these engines have? Do they usually make the recommended TBO if properly managed? Any reason why you wouldn't want to fly behind one?
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If you have access to ethanol free car gas that's what I would burn. My brother has a 172H (O-300 powered) and has burned about 300 hours worth of car gas in it. He just flew it from Seattle to Florida this year with all 4 seats full consisting of skinny Asian wife and their two kids. The kids are probably 90#s each. He weighs about 200.

He's flown it over the Cascades and the Rockies more than once at gross.

That late of an O-300 should be fine. No reason to avoid it. As far as being underpowered, a newer 172 won't be much different. Basically if you need more power than a 172, I'd just get an O-470 powered 182.
 
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I loved my '57 straight tail with an o-300. Had the prop dynamically balanced and it was like flying behind a sewing machine. Smooooooooooth.
 
bnt83 said:
If you have access to ethanol free car gas that's what I would burn. My brother has a 172H (O-300 powered) and has burned about 300 hours worth of car gas in it. He just flew it from Seattle to Florida this year with all 4 seats full consisting of skinny Asian wife and their two kids. The kids are probably 90#s each. He weighs about 200.

He's flown it over the Cascades and the Rockies more than once at gross.

That late of an O-300 should be fine. No reason to avoid it. As far as being underpowered, a newer 172 won't be much different. Basically if you need more power than a 172, I'd just get an O-470 powered 182.
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Fortunately, we do have ethanol free mogas on the field where we are based so we will certainly be using that the majority of the time. The plane already has the STC needed.
 
The only issue I've "heard" is cycling the motor, not good for training / touch and gos because it has a tendency to glaze the cylinders...cannot confirm this, but the "old guys" on the field always say this
 
mrkbbd said:
The only issue I've "heard" is cycling the motor, not good for training / touch and gos because it has a tendency to glaze the cylinders...cannot confirm this, but the "old guys" on the field always say this
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Right...... :rolleyes2: The O-300 has the exact same cylinder assemblies as an O-200, which are installed on what used to be the #1 training airplane in America, the Cessna 150.
 
mrkbbd said:
The only issue I've "heard" is cycling the motor, not good for training / touch and gos because it has a tendency to glaze the cylinders...cannot confirm this, but the "old guys" on the field always say this
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They're wrong, what does the glazing is over rich operations.
 
weirdjim said:
I don't happen to believe that is true, but if you explain why I might be converted.

Jim
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Too much fuel washes away the film of oil which lubricates the rings which allows the chrome rings to really polish the steel bore, also when really rich at high power &heat you can get some hardening effect as well.
 
cmathis said:
My club is considering purchasing a '67 Cessna 172 with the O-300 engine. I have read and heard they are prone to lead fouling and to be certain to properly lean on the ground and in the air. What other gremlins do these engines have? Do they usually make the recommended TBO if properly managed? Any reason why you wouldn't want to fly behind one?
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That lead fouling has nothing to do with something inherent about the engine and everything to do with how people (fail to) lean the mixture.

I owned a 1966 C172G with the same Continental O300 for 7 years and never had a problem with lead fouling. I lived in Texas so I flew it at 5000 to 7000 ft on XCs and maybe 1500 in the pattern.

I lean for peak RPM on every flight. However, the older Cessnas came with those dumb mixture controllers with the inverted-V clips instead of vernier-style controllers. Those old-style ones SUCKED and it was really hard to fine-tune them and that was the first thing I replaced. If your club's target plane has that controller, I'd suggest they replace it because it may just be enough of a PITA to cause pilots not to touch it.

So perhaps that controller is partly responsible for that undeserved reputation about the engine.
 
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cmathis said:
My club is considering purchasing a '67 Cessna 172 with the O-300 engine. I have read and heard they are prone to lead fouling and to be certain to properly lean on the ground and in the air. What other gremlins do these engines have? Do they usually make the recommended TBO if properly managed? Any reason why you wouldn't want to fly behind one?
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Where is the airplane located? And who did the last overhaul?
The O-300 is a good engine, and only 5 hp lower than the O-320. If Gann did the last OH it will be a very good engine.
They are no more prone to lead fouling than any other smaller engine. Just lean it on the ground. Then use Carb heat when you're suposed to, and there won't be any ice issues.
It's a Conti. and all the Conti.s that I'm familiar with manufacture carb ice from dry air. But that's what carb heat is there for.
 
Flew one a little at work a few years back

Smooth and gutless.

Don't recall I ever being laid up in the shop.

That said I wouldn't rent that plane unles it was a me + 1 mission, and the thing rented dirt cheap.
 
My wife cannot stay awake in my 66 G model 172. This year I put the REM37BY plugs in mine but regardless I've never had an issue with lead buildup and I clean my own plugs. Like my previous O-200 I lean the heck out of it on the ground and run it about 85* ROP in cruise.

A friend has a 65F model and although mine runs more smoothly, his plane is a few knots faster than mine. We actually went to altitude, did timed climbs and then leveled off and he pulled away from me at the same indicated RPM.

I can get my burn rate down to 6 and change per hour at 2300 and leaned out.
 
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