I've got a Cessna 185 on Aerocet Amphibs with an IO-550. I installed the engine and prop nearly 400 hours ago. Texas Skyways Conversion. Kosola Engine Mount. I have always had a considerable vibration at high rpm. Reduce the rpm to 2300 smooth as silk. Hartzell removed the prop disassembled it, re-aligned it, static balanced it. Still vibrates. Anyone running the same set up or knows someone that is running the Hartzell with the IO-550 on a 185 that I can talk to?

You may want to find a balance shop that uses EVXP or similar. The new magic boxes can pinpoint exactly what is the cause. Crank, Cam, Accy Drive etc.
No guesswork, they hook the monitors up to your engine do a 20 sec ground run and read the results. The little cheap prop balance boxes wont tell the whole tale, but many shops have machines that will.

Thanks for the tips. I'm to the point of selling it and buying a McCauley. The prop pulls great and it very quiet, but the vibration is shaking my plane apart. I actually switched props and put a McCauley 401-C on it and flew it just to see what would happen and the vibration was gone. It is definately prop related. Hartsell basically said there is nothing more they can do.

Did you have the engine/prop DYNAMIC balanced? That's the key to smooth setups. If that doesn't work, send the prop back to Hartzell and buy an MT composite prop. MUCH lighter, reliable, and SMOOTH. And, it won't be subject to Hartzell's plethora of AD's.

MTV

Ive got the IO-550F and 82inch Super Scimitar. Smooth at high revs, not smooth at 2300 or lower. We decend at 2200, somewhere here I also have an alternator belt harmonic. I like the thrust from my Scimitar and prop hasnt picked up any nicks in over 1500 hours. How was the pull from the 401?

Yes, it was dynamicaly balanced, we are going to hook up the equipment and fly it this week. Will keep you posted. I couldn't tell the difference in the pull on the Mac or the Hartzell....pretty much the same. I didn't fly it but a few minutes, a friend was nice enough to let me take it off of his plane and try it on mine. And yes, my Hartzell too looks brand new after 400 hours...no nics...even the Hartzell rep was amazed at how good the prop looked.

Digger,
I have the same setup but find the higher rpm (2550) results in the smoothest operation and is what the conversion info suggested. I think MTV comment on having a dynamic balance from a reputable shop will get results. I have 1000 hours on that engine/prop combo with one prop overhaul about four years ago. Hope it works!

Is it directly releated to RPM and not power? What is the vibration level at High RPM and low MP? I can cave in the front left motor mount at full power and now the pulses go into the airframe. I upgraded to the 6 mount system in my 206 and need the replace the front, front left mount already after 600 hours.

Be sure that the prop is indexed properly, I have seen shops do it wrong, and it will cause lots of vibration with the blade out of phase with the firing order. On that setup, you should have the downward blade horizontal, when you are at TDC.

I'm sure tip tracking and blade pitch has been checked, but just in case . . .

Place a stand with pointer next to prop tip with blade almost touching pointer. Mags off (duh), turn prop so opposite blade is next to pointer. Should be same distance or very close, less the 1/8" or mfg's spec.

With each blade horizontal, measure angle at same station using digital inclinometer or protractor w/level.

If either of these parameters are out of spec it will cause vibration.

There are many other things that will cause vibration too, from bad or broken motor mounts to a poorly weld repaired cylinder that raises compression on one jug (yeah, I ran into that once while balancing a prop on a friend's 185). But since the OP changed props and a different prop worked just fine, then one would think this issue should oughta be with the prop in question and not the airframe.

Well my problem was resolved this week. I took my plane over to Texas Skyways whom I had purchased the engine and prop from. They owned the STC for the engine/prop configuration on the 185. They were helpful in that they tried to balance my prop to no avail, they switched out my prop with another identical prop and we still had vibration. We finally put a McCauley prop on and again no vibration at all...smooth as silk. So 13k later problem resolved. Guess we will never know what caused the vibration. It wasn't my individual prop because the identical one did the same thing. It isn't the prop design on the 185 on wheels because there are many operating with no problems. The only thing we can come up with is an interaction between the configuation on floats...only a theory but one that we would never know without considerable research. Research that I wasn't willing to spend the time on. Thanks to everyone for all of the help and input. BTW....I have a Hartsell prop with 400 hours on it for sale.