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Continental O-300-D Pros/Cons

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Continental O-300-D Pros/Cons

Old 25th Apr 2012, 15:42
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Continental O-300-D Pros/Cons

Could you please advise on the pros/cons of a Continental O-300-D with regards to running costs, carb ice problems etc when fitted to a Cessna 172G or H. I'm looking at buying a 172 for a group and am tasked with finding out the above information from those with experience, so any help would be gratefully received! How, in the real world, would such an engine compare to a later Lycoming O-320, and should we avoid the N and go for the M model instead of a G or H?

Many thanks, PP.
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Old 25th Apr 2012, 15:52
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there was a discussion a few years ago about this engine:


Kind regards,
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Old 25th Apr 2012, 23:07
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The earlier C-172 models fitted with the 0-300-D engines are delightful gentle aircraft with a very very smooth engine. Of course slightly underpowered (hence the upgrade in later models from the 145hp in the 0-300-D to 150hp in the first of the lycomings and then 160hp in later models still. These later models were eventually heavier and hence needed the bigger engine to maintain (or slightly improve ) the performance.
An early model with the 0-300-D is a very cheap and good way into 4 seat touring aircraft(but watch the (W and B). Cheap to buy, negative depreciation, easy maintenance,happy on mogas, cheap to insure, occasional problems with sticky exhaust valves but with considerate engine management there should be no problems.
Go for one.
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Old 25th Apr 2012, 23:13
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Put the carb heat to "hot" when reducing power to land, and don't move it unless you are vacating the runway, or after application of full power on the go-around.

The 0-300 is an 0-200 with an extra row of cylinders, and very prone to carb icing.

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Old 26th Apr 2012, 20:41
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O-300D vs Lycoming

My 172H had a delightfully smooth six at the front, but it did suffer various costs I didn't expect. Because it hadn't flown enough when I bought it the gudgeon pins needed replacing (white metal in the filters). Not cheap. With six cylinders overhauls cost more, of course.

On early engines there was an AD on checking play in the square lug that connected oil pressure pump to camshaft. If it ends up round, no oil is pumped - very expensive. Make sure your engineer checks this.

If you go for a 172H and find you don't have enough power, once you've built up a (quite large) engine fund, you can convert everything firewall forward to 180HP Lycoming O-360 with a kit from Air Plains - see www.airplains.com. It's virtually as cheap as having your engine zero-timed.

I did that 300 hours ago and the performance is better than a new 172 - because the airframe is lighter with more power. With the 40 degrees of flap you get on the older models you can get in and out of anywhere.

Good luck in your purchase!

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Old 26th Apr 2012, 20:56
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The 0-300 engine is a peach really.Smooth and nice-sounding.

Contyplodicus engines are better for low utilisation aircraft when compared to Lycosaurus because the cams are on the bottom of the engine sitting in the oil. Low utilisation Lycos from experience are prone to corrosion on the cams and followers. Once the surfaces corrode too far the degeneration is a bit rapid.

My old H model was just lovely but my favourite model with the leading edge cuff is the M model, slightly faster and sweeter handling.

Recently flew a 172 H fitted with a diesel engine and it was sweet as!

0-300 powered 172's are cheap to buy and run so go for it, you will all fill your boots with flying experiences. Good luck.

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Old 26th Apr 2012, 21:35
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I’ve been lucky enough to be able to fly a Cessna F172H for several years now. The engine has always performed as expected and reliably delivered a good ride.

I can only agree with everything Overandout says about the 172H but that given current issues around alcohol in mogas recommend you to stick to using 100LL. For permit aircraft UL91 has been agreed for use in the 0-300 by the LAA, however it’s not clear what the situation on this is for C of A machines such as the 172 http://www.lightaircraftassociation....aded%20AAN.pdf

If the engine in the aircraft you have in mind is low hours but high calendar time (10 years) I recommend the pre-purchase inspection of the aircraft includes a check that the mags and any other time lifed items have been serviced or replaced, that the carb float service bulletin has been implemented and if the engine is “on condition” past 10 years that AD 94-05-05 has been carried out.

There is Cessna 172 group on yahoo who might also have some views that can help you cessna172 : Cessna 172 - A place to talk about Cessna 172's

The owner of an O-300 engined 1959 Cessna 172 has a lot of information about owning and operating the aircraft at Cessna 172 G-BSEP - David Williams flying homepage

My favourite feature about the O-300 installation on the F172H is the really big hatch in comparison to later models for getting at the oil filler and dip stick. It makes the oil check during the walk round very easy and the occasional topping up of the oil can be done directly from a litre bottle without the need for a funnel. You also get a really good view of the general condition of the engine crankcase and equipment attached to it.
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Old 27th Apr 2012, 07:59
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Thank you to all who have taken the time to reply. Some very useful information. I am still researching this as I can't yet make a decision on whether to go for a cheaper H or pricier M or P. So anything more is welcome. Thanks again.

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Old 27th Apr 2012, 08:23
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Isn't fuel consumption the most important variable nowadays? I operate a 172M with an O-320-E2D purely on Mogas with an STC and the fuel consumption is exactly 28l/h for my cross-country flying and in average 32l/h for the pattern flying of others.

The 150HP O-320-E2D is a very solid powerplant with low compression. I would recommend the 172M over the 172N with 160HP due to engine reliability. In my experience, the 172N does not perform any better than the 172M, mostly due to its increased weight. Make sure the crankshaft AD is complied with on the O-320-E2D.

Ethanol in Mogas is indeed an issue. The STC allows for 1%. Shortly after the introduction of E10, I did see Mogas with up to 2% but that was only for a short while. When it's more than 1%, I just mix it with AVGAS to stay under 1%.
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Old 29th Apr 2012, 00:12
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A very good point made about fuel consumption by achimha. According to my POH in the F172H the O-300 will use 7 us gals (26.5 litres) per hour cruising with 60% power (2300rpm) at 2500ft. This is for a new fully loaded aircraft. Cruise and Range Performance | Facebook

In my experience remembering to lean and careful engine management can better this for general day to day leisure flying between 2 and 3 thousand feet around the local area at 90knots on 100LL AVGAS.

The led in 100LL will occasionally foul the spark plugs causing problems from rough running on a magneto check during the pre-take off engine checks. Just running the engine on both magnetos at full power for a couple of minutes will usually clear this.
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