Tom, I will dig around in my things and see if I can fine the paperwork for the change from 75 to 85, seems like I had it years ago.
The changes are to recalibrate the dip stick to indicate 4 1/2 qts, and change the jet in the carb to allow more fuel, change the data plate on the case, and change the prop to one specified for the 85. And the paperwork. From what I have read, Mr. Weick stated that he used the 75 rather than the 85 at a time when both were available, because the 75 develops it's peak torque much earlier in the power curve and the 85 does. It's peak torque is more toward the end of the power curve. The 75 turns at a slightly lower RPM with the 75 prop than does the 85 with the prop(s) for the 85. The 75 props are longer with a higher pitch which holds max rpm to within 75 hp limits. Mr. Bob German who used to own Skyport Ercoupe Services, told me that the 75's will turn up just as many RPM's as the 85's, so just put a prop on it that is specified for the 85 and fly it. I concluded that the real difference, regardless of what your hp engine is labeled, is the prop and the rpm at which you turn your engine. So, why not just reprop it for more performance in the area that you want, be it climb or cruise. I am familiar with the McCauley metal props. For the 75 it is a 7351. For the 85 it is 7150 for standard or cruise, and 7148 for takeoff, climb, and high altitude. Mr. German said that a good comprimise would be the 7149 (a prop that the 90 hp SuperCub uses, I believe). Additionally, I read a string of correspondence a few years ago about the performance of Coupes at high altitude out West and that some persons had changed to 0-200's. At my local airport, there is an 0-200 coupe and I can tell you that this particular one has absolutely NO performance advantage over the 85 hp coupes on our field. He has tried several props and it still does not perform as well as the 85 hp coupes here. And he has had a world of trouble with it. Based on this experience, I would not consider that change. Lastly, I read the letter of the coupe owner out West who said he solved his high altitude climb problem very well by simply installing the 7148 climb prop and quote, "that he did not have to change to the 0-200, that his performance with the climb prop was just great and he recommends that change for better performance rather than swapping 0-200 for C-85." If you will get your prop repitched to 48 or 49 inches and changed from the 75 hp diameter to the 85 hp diameter which is 69.5" to 71" you should accomplish what you want in the way of improved climb performance and high altitude performance. Grover 99398 On Tue, 16 Feb 1999 22:55:47 -0800 "Tom Laird-McConnell" <[EMAIL PROTECTED]> writes: >Can anyone out there help? > >-Tom > >-----Original Message----- >From: Jesse bennett [mailto:[EMAIL PROTECTED] >Sent: None >To: [EMAIL PROTECTED] >Subject: Trying to locate SB > > >Tom, this is Jesse Bennett, 415-D owner from the Eastern slope of the >mountains (We met at 'Arlington 98'). I'm trying to track down a copy >of >Continental Service Bulletin M47-16 dated June 7, 1948, it is for the >conversion of a C-75 engine to a C-85 (and I could use the extra HP up >here >in the mountains!). I was wondering if you know of any other 'coupers >over >there who might be able to fax me a copy?, I would really appreciate >it! >Thanks - JESSE > > > FAX- 1-509-997-4410 > > ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866]
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