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At 07:58 AM 3/16/2005, Dan Mooney wrote: >I want to upgrade the engine to 85hp. I was told that it requires a Carb >Jet change and remark the tach? Is there a prop change? Technically, you have to remove the C75 carburetor and replace it with a C85 carburetor. Practically, the differences between the carbs are minor. The venturi and main fuel jet are different. Be sure to confirm that the carb meets the specifications for the C85 and then remark the carb accordingly, or some IA may refuse to sign off the plane at a later date. Then we come to the issue of the engine. If it's a C85 you need a C85 data plate. Otherwise some IA may refuse to sign off the plane at a later date. As someone else pointed out, the prop requirements are different as wall. A C85 will not produce much more than 75 hp coupled to a C75 prop as it will not be able to turn enough RPM. And, if you have a C85 with a C75 prop, well, some IA may refuse to sign off the plane at a later date. also, the length limitations are due to vibration concerns, so you really don't want to tempt fate. C85 crankshafts are easy enough to break and too expensive to replace. Assuming you have a C85 carb, dataplate and prop, then you can remark the tach, otherwise some IA may refuse to sign off the plane at a later date. That said, I'm sure there a bunch of coupes out there flying around in a state where some IA may refuse to sign off the plane at a later date.... John Cooper Skyport Services PO Box 249 4996 Delaware Tnpk Rensselaerville, NY 12147 518 797-3064 ========================================================================== ==== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/
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