Alaskan Tin Can,
I'm not sure that I'm an authority by any stretch of the imagination, but I did work on McCauley propellers for more years than I care to remember. I'm going off memory here, and apologize in advance for any erroneous information.
The C58 and C66 have the exact model of blades. (90AT-X) The C58 can be restamped by a propeller shop as a C98, with the addition of the dual spring pack for sprayer operations and other minor details. (pitch settings) The C66 is the same hub as a C50, with the exception that you run 90A-X blades. The 90AT and 90A blades are very near identical. In fact, they have the same width and thickness minimums.
The C58 is doweled for the 520 engine, the C66 for the 470. With field approvals, both have been successfully run on PPonk engines. They may be older props, but these things are great for taking a prop strike. Where a newer style (C200 series) blade have the butt doweled for the actuating pin (base), these older blades have a steel ferrule that screws on to the threaded blade. These blades are much easier to straighten for a prop shop. At least they were for me.
Because the C58 and C66 are doweled differently, the spinner/backing plate combinations are not the same. I saw many more C58 hubs fail Eddy Current Inspection as opposed to C66, due to the fact the C58 had higher horsepower to it. C98's in a crop duster were cracked quite often.
The steel ferrule threaded on these blades can be used a maximum of 4 times. It is removed for inspection at overhaul and never reused on the same blade. It would be impossible because of the high torque required to get it back in the exact position required. A different ferrule is torqued on the blade and then indexed and drilled in a jig/fixture. The new hole for the actuating pin must be a minimum of 1 inch edge distance from another previously drilled hole. The ferrules are becoming extremely rare, and these props take much more time to overhaul and assemble. While there is nothing wrong with them, I question buying old school when you will eventually be paying the price.
The C201 and C203 are the exact same hub and are totally interchangeable by a propeller repair station.
The C201 had 90DA-X blades, where the C203 has 90DCA-X blades. The C203 in my estimation is worth slightly more.
It is a similar comparison between the C50 and C66 older threaded style blades mentioned in first paragraph. The blades are basically the exact same. I won't point out the difference here, as the difference is only something you could discover in a prop shop setting. For all intent and purposes, there is no difference performance wise between a C201 and C203 propeller.
The C204 is again a different prop. It takes 90DCB-X blades. The hub is doweled yet again differently. It is designed for the U engine, which turns 2400 RPM. As a result, where these blades are similar in many ways to the 90DA and 90DCA blades mentioned above, the butt of the blade itself is doweled and pinned differently in relation to the blade angles. The reason for this, is because it was designed for a slower turning application, the low pitch setting is much steeper. You will notice on the McCauley application guide, that a full length seaplane prop for a U engined airplane is 90" typically. If my memory serves me correctly this could only be cut back to 88.5 in a seaplane application for repairs. I believe North West Propeller in Washington has an STC to run a 204 in place of a C201 or C203, but I never recommended it, due to the fact it required a different spinner/backing plate combination and it was necessary to have the low pitch stop changed in the cylinder to accommodate the different low stop angle required to turn to the higher rpm required by those engines in relation to the slower turning U (2400).
Now for the oil-fill versus non-oil filled 2 bladed threaded propellers.
I doubt if there are any C58 or C66 propellers out there any more that have not been oil-filled. It was a great mod over the grease. There is a continual lubrication of the bearings/races. They do often times leak as the o ring tries to work itself out where the two notches in each end of the hub are that the lock ring fits into. red dye is added to the oil to differentiate between engine oil. It's supposed to be an aid in the crack detection of the propeller.
Non oil versus oil filled 2 bladed threadless propellers (C200 series)
I don't think I would buy a used 2 blade that hadn't been oil-filled. The oil-fill modification kit is very expensive, even for a prop shop. While these props are much easier to overhaul than the threaded series, it still gets pretty expensive to overhaul and oil-fill. Add that on to your initial purchase cost and you just as well buy new. It doesn't take very many years for the grease to break down in a grease filled prop (non-oil filled) and pretty soon its making a mess everywhere. They don't heal themselves and pretty soon you swear its oil coming out, which it basically has become.
I love the C203 oil-filled propeller with the slick new balance ring and the modern McCauley blade decals. (I hated the flying brick)
I'm putting one on my 1960 Cessna 182C, currently a work in progress. It has a great history, I have ridden behind it to many a "Maule Only Strip"
in the Frank Church Wilderness with the "Flying Hawkes". It wouldn't work on his PPonk Backcountry Tamer, but it's been there and done that. A great propeller!
I hope I have not added to any confusion out there.
Richard
