Which O-235 can I put in my J-3? (2024)

Stay away from it. Put an 0-200 in it. 100hp with little weight gain. But that just my opinion.

John

Ulpilot,

Yes, that is essentially correct.

John Scott

My little PA-11-90 started out as a J3C-65.
It was wrecked in 1948 as a crop duster and stayed in a barn until the 1990s when she was totally rebuilt as a PA-11 using Atlee Dodge Stcs.
I have the C-90-8. So the plane weighs less than 800 empty. But I have no electrical. I land and take off in 300 feet with two folks and 18 gallons on board.

Back when I was flying a no-flap 125hp PA-12, there was a guy with a 115 horse converted J-3/PA-11 and he had flaps. He was always cutting it close on his gross weight, but he could take-off about the same as I could without flaps. About 350 to 400 feet.

The J-3 /PA-11 series need to be kept light or they dont work so great. Their tubing is lighter and further apart so they really don't like big heavy things hung on them.

A friend of mine in Juneau had a C-90 J3 that was very light - and it could really get off the ground. Try as I might, I couldn't beat him off the beach with my PA12-150 with flaps, even after throwing the rear seat cushions and everything else out on the sand! He couldn't beat me either though - it was a frustrating draw - trial after trial! But with a passenger in back, the picture changed completely - - For short and soft field, nothing, but nothing matters as much as weight, I think! As I look back on it, he always flew solo from the front seat, and I bet if he were in back and optimally trimmed he could have got off even shorter.

My 12 was pretty nose-heavy, I bet it would have done better driving from the back too! Has anybody experimented with take-off distance or cruise speed soloing from the back of a 12-150 with standard length engine mount?

You would cruise faster with an aft CG due to the change in angle of attack on the wing.

But, I wonder about taking off. If your tail is light is comes up faster and that reduces the drag from the first part of the take-off run. Then you swing it back down (nose up) for rotation. So having a light tail might be better. But on landing having a heavy tail helps you stick the landing and stop faster.

J-3 w/235

Yes,
there is an STC for a J-3 with a O-235 C1 115 HP. I have one. It was done back in the sixties though. The engine mount is a PA-18, it has a gallon header tank similar to a PA-18 and 1 18 gallon wing tank in the left wing. I had taken all the electrics off. My EW is in the upper 700's. I can solo from front or rear. Flies great. However I only get about 2.5 hours flight time per tank. The plane is similar to the PA-18 105 Special now.

I'll see if I can find the STC number on the 337.

Joe