O-300s - Love em? Hate em? Typical maintenance costs and overhaul cost

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Ceraphiim

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TimRans
Howdy Folks! I have found several threads on here throughout the years about the O-300, but not where all these answers are lumped together. I know very little about them having little experience running or working on them. So tell me what you know! Do you love it or hate it? What are the common problems you find, and what is the total cost of the typical overhaul on one?
 
there are people that love them and people that hate them. all engines have bad things and all engines have good things. im sure tom will jump in, he knows them inside and out.
 
Good, simple engines. Basically a 6 cylinder O200 (uses the same cylinders). Parts are reasonable. Flew an old 172 with the 145hp O300 and it was similar in performance to the O320s (150hp) and ran much smoother.
 
unsafervguy said:
there are people that love them and people that hate them. all engines have bad things and all engines have good things. im sure tom will jump in, he knows them inside and out.
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That sums it well enough.
 
I've owned one for 18 years now and like it well enough. Biggest recurring problem has been sticky exhaust valves/guides. I recommend they be checked every 100hrs, and cleaned/reamed if necessary.
 
0-300 is typically smoother running, uses a little more fuel than its 4 cyl rivals and has a factory reccommended 1800 hr TBO vs a 2000 TBO for an 0-320. Overhaul cost a little more due to two more cylinders and there are more possible failure points due to the extra cyls, valves, rods etc. They do sound a lot healthier than a 4 cylinder engine. I wouldn't be afraid to fly behind one.
 
I had one for ten years (1963 C172D) and found it reliable and relatively inexpensive to maintain. I did have two stuck exhaust valves within a couple of months of each other and did a top overhaul with six new ECi Titan Cerminil cylinders that have valve rotators and never had another stuck valve. A lot of owners complain about corrosion of the magnesium oil pan, but mine showed no sign of corrosion either internal or external. Also, some owners say the O-300s are more susceptible to carb ice, but I didn't find that to be true.
 
Brad Smith said:
0-300 is typically smoother running, uses a little more fuel than its 4 cyl rivals and has a factory reccommended 1800 hr TBO vs a 2000 TBO for an 0-320. Overhaul cost a little more due to two more cylinders and there are more possible failure points due to the extra cyls, valves, rods etc. They do sound a lot healthier than a 4 cylinder engine. I wouldn't be afraid to fly behind one.
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TBO moot point, no one comply's
 
Stan Cooper said:
I had one for ten years (1963 C172D) and found it reliable and relatively inexpensive to maintain. I did have two stuck exhaust valves within a couple of months of each other and did a top overhaul with six new ECi Titan Cerminil cylinders that have valve rotators and never had another stuck valve. A lot of owners complain about corrosion of the magnesium oil pan, but mine showed no sign of corrosion either internal or external. Also, some owners say the O-300s are more susceptible to carb ice, but I didn't find that to be true.
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0-300-A (145) getting hard to find, 0-300-D plentifully, but expensive $ 7,000 - no core

oops..
http://www.aircraftspecialties.aero/o300d-crankshaft-653382/
add 1800 for core.
 
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I'm in the love-it camp. We ran one from 0 to 4400 hours smoh before it started making metal, in a 172F. Noticeably smoother vs the 4-banger Lycs.
 
enjoyed ours
except for all the valve sticking (very distracting at night on an XC)
this was 1970's 80's...before most people knew how to lean an engine.
and older fuels if that had any hand in it
 
Run Marvel Mystery Oil in the fuel and it pretty much cures the sticking valve problem. I like the O-300...
Right now I have a Cessna 175 with the GO-300 and I really like it. It performs well.
 
GRG55 said:
:yeahthat:



Can they be run on mogas? And would that make a difference for the valve sticking? Weren't they originally were intended to run on 80/87?
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Like a blend, 2 gallons of 100LL to 3 gallons of 92 mogas.
 
Stan Cooper said:
I had one for ten years (1963 C172D) and found it reliable and relatively inexpensive to maintain. I did have two stuck exhaust valves within a couple of months of each other and did a top overhaul with six new ECi Titan Cerminil cylinders that have valve rotators and never had another stuck valve. A lot of owners complain about corrosion of the magnesium oil pan, but mine showed no sign of corrosion either internal or external. Also, some owners say the O-300s are more susceptible to carb ice, but I didn't find that to be true.
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We bought ours from a retired corporate pilot/A&P/IA, who did an annual each year, and didn't fly it. Due to the short run time at annual, and the sitting about, the water that collected in that pan caused serious corrosion. We didn't have to replace it, but another year of disuse and it would have corroded through. We did an overhaul on it, had the cylinders bored (they had rust as well.) Putting 300 hours a year on it certainly stopped that, and it belongs to an FBO where you can rent it now.
 
Like pretty much every other engine it's more about how they were taken care of than the design or manufacturer. My only complaint is they are pretty thirsty for the HP they produce. While it does have more cylinders than an O-320 they are a little cheaper which helps offset the added quantity.
 
What other airplanes used the O-300s? I see you guys mentioned the 172.
 
Kenny Phillips said:
We bought ours from a retired corporate pilot/A&P/IA, who did an annual each year, and didn't fly it. Due to the short run time at annual, and the sitting about, the water that collected in that pan caused serious corrosion. We didn't have to replace it, but another year of disuse and it would have corroded through. We did an overhaul on it, had the cylinders bored (they had rust as well.) Putting 300 hours a year on it certainly stopped that, and it belongs to an FBO where you can rent it now.
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Oil sumps can now repaired. If it does not have a hole in it.
 
Grum.Man said:
Aeronca Sedan
Cessna 170
Some Maule M4's
Bellanca 14-13-2

Those are the ones that come to mind quickly. Depends if you want to count the Lycoming 145
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You missed the obvious ones. :)
Baumann Brigadier
T-41 Mescalero
Meyers MAC-145
Taylorcraft 15
Temco TE-1A
GO-300
Cessna 175
Goodyear GZ-19 and GZ-19A

Good 'nuff for a blimp, good 'nuff for me.
 
Capt. Geoffrey Thorpe said:
You missed the obvious ones. :)
Baumann Brigadier
T-41 Mescalero
Meyers MAC-145
Taylorcraft 15
Temco TE-1A
GO-300
Cessna 175
Goodyear GZ-19 and GZ-19A

Good 'nuff for a blimp, good 'nuff for me.
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The 175 has a geared variant.
 
Only downside of O-300 is extra costs for overhaul and maintenance with 2 more cylinders and less power than a Lycoming O-360. Thus the reasons why it's obsolete in favor of the IO-360 or O-360 with more power and only 4 cylinders. Six cylinders are smoother, at least the ones I've flown.
 
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NordicDave said:
Only downside of O-300 is extra costs for overhaul and maintenance with 2 more cylinders and less power than a Lycoming O-360.
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You want to compare overhaul prices, then compare costs of like items
0-300-D are around $25k
0-360 are about $45k
(overhauled)
Plus the cost to convert.. $40-60K

what does 4 new 0-360 cylinders vs 6 new superior cylinders today?
 
Had a 1962 ,172 loved it never a . bit of trouble
 
NordicDave said:
Only downside of O-300 is extra costs for overhaul and maintenance with 2 more cylinders and less power than a Lycoming O-360. Thus the reasons why it's obsolete in favor of the IO-360 or O-360 with more power and only 4 cylinders. Six cylinders are smoother, at least the ones I've flown.
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Don’t forget the lack of critical parts like replacement crank shafts.

Aside from the occasional sticking valves, the O-300 is a great running engine. But when you have to send it off for overhaul, you best hope the crankshaft is within tolerance.
 
Fearless Tower said:
Don’t forget the lack of critical parts like replacement crank shafts.

Aside from the occasional sticking valves, the O-300 is a great running engine. But when you have to send it off for overhaul, you best hope the crankshaft is within tolerance.
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Good point.

Also overhaul costs from Corona Engines with new Superior cylinders are $16,795.00 for O-360 overhaul and $22,925.00 for O-300. Almost worth an STC fee for upgrade consideration.
 
I've only flown behind one once, but I liked it a lot. Didn't have excess power, by any means, but damn those engines are smooth.
 
Bellanca 14-13-2 Cruisairs have Franklin six cylinder engines, Cruisemasters have O-435 Lycomings or O-470 Continentals but no Bellancas have O-300s.
 
NordicDave said:
Good point.

Also overhaul costs from Corona Engines with new Superior cylinders are $16,795.00 for O-360 overhaul and $22,925.00 for O-300. Almost worth an STC fee for upgrade consideration.
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I doubt that these are realistic prices.
 
I've flown behind mine for around 14 years now and lean rigorously. I've had zero issues with carb ice or sticking valves. Mine consumes oil, more as of late, we haven't figured out exactly where yet. The old pushrods with the swedged ends and no springs are notorious for leaking, so if I keep my bird and O/H it she will get the Real Gasket mod for each cylinder (mod works, 1/2 my engine has them). I've replaced 3 cylinders over the years and am about to replace a 4th.

She is super smooth as others have said and has been reliable. Pull the back seat out and wheel pants off and save about 40 lbs payload for higher elevation. Used that tactic last year in the high country and she performed remarkably well up to 12,500 solo with gear. On fuel consumption, properly leaned I routinely see 6.5 GPH. I think I was in the high 5's when in Colorado at a few points like Cumbres and La Manga passes.
 
iflyvfr said:
I've flown behind mine for around 14 years now and lean rigorously. I've had zero issues with carb ice or sticking valves. Mine consumes oil, more as of late, we haven't figured out exactly where yet. The old pushrods with the swedged ends and no springs are notorious for leaking, so if I keep my bird and O/H it she will get the Real Gasket mod for each cylinder (mod works, 1/2 my engine has them). I've replaced 3 cylinders over the years and am about to replace a 4th.

She is super smooth as others have said and has been reliable. Pull the back seat out and wheel pants off and save about 40 lbs payload for higher elevation. Used that tactic last year in the high country and she performed remarkably well up to 12,500 solo with gear. On fuel consumption, properly leaned I routinely see 6.5 GPH. I think I was in the high 5's when in Colorado at a few points like Cumbres and La Manga passes.
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Greg, when I replaced all the cylinders in my O-300 with ECi Titans I also installed the Real Gaskets pushrod tubes. It was definitely a worthwhile mod; the pushrod tube oil leaks stopped completely.
 
I have a 1956 C172 and put the engine in for overhaul soon after purchase considering it only had about 550 hours, but had not been overhauled in 58 years. I replaced the starter with a sky tech STCd replacement, high output alternator, overhauled carburetor, overhauled bendix mags, new ignition harness, and all new millennium cylinders. The camshaft and crankshaft were well within tolerance and the counter weights were re-bushed. I did find some interesting issues. The magnesium oil pan did have some corrosion, but was not excessive. It had 6 rocker arms that were the wrong part number. The rocker arms for the exhaust valves have oil channels on both sides, but the intake rocker arms are not supposed to have this feature. We called continental and they would not approve the channeled rocker arms for the intake valves. An advisory circular mentioned the correct rocker arm positions for the exhaust valves, but there was nothing about using the exhaust rocker arms on the intakes. Apparently, this was done a lot with overhauls in the past, but not approved. I was able to find the correct rocker arms for the intake valves at $90 a piece ($580 new from TCM) and paid $50 a piece to have them refaced and re-bushed. The surprise was the magnesium engine mounts. Once they were torqued, we went back the next day to re-torque and it would not hold at the correct value, so upon inspection, we found that the flange holes that bolted to the engine were breaking apart. I decided to replace the mounts with new parts and they were $5,300 for the set. This was an important find and well worth the investment, considering a failure could have been catastrophic. The total cost for overhaul was just under 30k and I was getting a significant break in labor. I don’t know if these are common issues, but well worth looking at during the overhaul process.
 
I owned a ‘64 Skyhawk C172E with an O300D. Secondly a C150 the O200A.
Presently a 68 Cherokee 140 with a O320 E2A.

first; The O200 and O300 were no smoother than the Lycoming. Sorry, could just never get mine that smooth. Even though I had it overhauled twice, second time with weight matched pistons. Two overhauls on the O200 were essentially the same. Never got more than 1,100hrs without pulling a cylinder for valve rework. Leaning was essential with 100Ll. MMO seemed to help but in retrospect was likely just a bandaid approach. My only experience was with old Continental or new Millennium cylinders.
At the first overhaul, the otherwise serviceable crank shaft was rendered unserviceable by an undetectable (circa 1963) flaw in the forging. 1994 x-ray dectected it. A serviceable crank cost me $895 in 1994. Added 20% cost to my local shop o/h! No new cranks were available even back then.

Ive got several thousand hours in several other O300’s. None are noticeably smoother than the Lycoming 4cyls. As a CFI I’ve flown dozens. My experience is that the Lycomings are hands down better for reliability. My experience with O470’s, and 520’s further my feelings. The Continentals due to induction system design with carburetors is conducive to carb icing. Experienced it many times. Never with a Lycoming. My C150 on a cool cloudy humid day could ice up taxiing from the tie down to the active—- about 500yds. Once had engine quit at 3,000’ with 72deg oat, 55% humidity. Dead sticked it onto Rwy 6 at KCSG. Upon touch down the engine purred like a kitten. Surface temp was low ‘80’s over the asphalt rwy. Couldn’t duplicate it...

In 1991, My wife and I flew a local club Warrior to Mobile for my wife’s cousin’s funeral. Her uncle picked us up at the airport asked me if the Piper had a Continental or Lycoming engine. I was surprised at his knowledgeable question. I replied “a Lycoming “.
He said “That’s GOOD”! I asked why? He replied, “I worked for Continental for 27 years and know what they put into them” !!!
His words, not mine!
 
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Have a 57 Cessna 172. Another upside to 6 cylinders is if you have a cylinder that isn't doing it's part of the work you hardly notice.
 
Oh, you notice it alright!
I experienced my first cracked cylinder 4months after purchasing the plane. Taking off , I was immediately met with a 100rpm drop in climb rpm and unresolvable roughness. Like a fouled plug. (My first diagnosis). When I arrived at my destination, (short hop from avionics shop I’d visited), I pulled through the prop and was met with a dead cylinder. Mechanic checked other cylinders and found another had only 40psi compression. Two cylinders 40hrs after the first annual. OUCH! 1,300hr engine.
 
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