I thought I put this thread in the open forum, as it applies to the Cruzer, STOL and maybe also to the 650.

I understand that Zenith designed the CH750 for engines with a weight of up to 300 lbs. I also understand that Zenith approves a max. gross weight of 1,510 lb, if the max. g-load is reduced to 3.8 G.

The Lycoming O-320 is around 90 - 100 lb heavier than a Rotax 912, but has at least 150 hp and is plentiful available.

Most Rotax 912 powered CH 750s are in the range of 750 – 800 lb. Adding 100 lb for the O-320, we’d be at an empty weight of 850  - 900 lb.

1,510 lb max. gross – 180 lb full fuel – 900 lb empty weigh =  430 lb payload

430 lb payload would still be fine. Since the 900 lb assumption for the empty weight also appears to be a little bit on the high side, I would expect the actual payload to be more in the area of 450 lb.

On paper, it sounds as whether an O-320 might be a feasible option, the performance should also be great. Besides of the amphibious 750 on YouTube, I am however not aware of any O-320 powered Zeniths.

Are there other disadvantages, besides of the reduced useful load? Will it become nose heavy? How does it fly?

The Titan X340 with 180 hp, a stroked O-320, should also fit. This is the engine which is used in the popular Cubcrafter’s Carbon Cub and the new Kitfox STi. Not sure, if the Zenith can handle the hp and X340 will probably exceed our budget anyway. Still, for discussion’s sake – this should be an awesome engine for a Zenith. Or not?

Oliver