Engine conversion

[Dano"T"]

Re: Engine conversion

I have 2 BC12Ds 1 has a C85-8.... The other a C90-12... Approx same ew.the 90 outperforms the 85 by a noticeable margin. I run a McCauley 71-42 on the 85 and a Sensenich 76AK-2-40 on the 90. I bought the STC for the 85 upgrade and then did a 337 for the 90 since the FAA automatically allows 10% hp increase at the IA approval level. If your skeptical...then believe what you want...but the 90 is far more impressive on takeoff, climb than the 85. I have the benefit of being able to fly one, land and push the other one out and fly it right then....a great comparison. And I've had them both on floats and the 90 pulls much harder onto the step. I did try the Sensenich 76AK-2-40 (74" long) prop on my 85 once, but it would not turn it fast enough to make HP....topped out at 2150 rpm ..the 90 spins it 2475 on takeoff. The 71-42 is the optimum prop for the 85

[astjp2]

Re: Engine conversion

I have 2 BC12Ds 1 has a C85-8.... The other a C90-12... Approx same ew.the 90 outperforms the 85 by a noticeable margin. I run a McCauley 71-42 on the 85 and a Sensenich 76AK-2-40 on the 90. I bought the STC for the 85 upgrade and then did a 337 for the 90 since the FAA automatically allows 10% hp increase at the IA approval level. If your skeptical...then believe what you want...but the 90 is far more impressive on takeoff, climb than the 85. I have the benefit of being able to fly one, land and push the other one out and fly it right then....a great comparison. And I've had them both on floats and the 90 pulls much harder onto the step. I did try the Sensenich 76AK-2-40 (74" long) prop on my 85 once, but it would not turn it fast enough to make HP....topped out at 2150 rpm ..the 90 spins it 2475 on takeoff. The 71-42 is the optimum prop for the 85

Your prop differences in pitch and diameter will show the difference even on the same engine. I would do the o-200 converted to a -8 and slick mags and marvel carb. You get the full 100 hp and use a seaplane prop pitched to 42" will cruise 106kias at 2500 msl, not mph, KIAS.....verified with gps in a square flight pattern and it climbs at 1000 fpm up to 6k. Tim

[cvavon]

Re: Engine conversion

Will find out about props soon as 74/43 MC is coming off and 76AK-4 is going on that prop is 72/40 Sensenich will see how it pulls