rotate transmission 90degrees

Someone is building a helicopter.

Have you thought about the gearbox from something like what is commonly called a bush hog rotary mower. They are common in agriculture. Larger mowers easily put 100 HP thru them. Sorry, I have no idea if they come in different drive ratios. They are classified in HP ranges.

A rear axle and diff mounted vertically. Cut/modify as needed. The gears are in the diff to do the job needed.

Outboard motors have a connection on the bottom for the drive gear and whatnot. There is also a flywheel on the top of the engine. If, as someone else suggested, you are building a helicopter I would think an outboard engine would be an excellent choice for a powerplant. Great power to weight ratios and you could rig the propeller to the top of the engine with fair ease.

Harry

The homebuilt helicopters use a 5 or 6 groove pulley bolted to the flywheel of a two-stroke outboard. It is usually a Johnson or Evinrude 99.6 cid cross-charged(as opposed to loop-charged) V-4(85 to 140 hp)... there are manifold plates made to bolt to the bottom of the powerhead to accommodate the cooling and exhaust systems. You will need a closed-cooling system for flight, obviously(water pump & radiator), and a tuned exhaust (stinger, expansion tube, and muffler).

The bottom of an outboard is not a good place to drive much more than the water pump in this configuration. It is just a splined crankshaft, and would require some kind of full-bearing gearbox to be useful. Not very practical when the cooling and exhaust is confined to the same area.

Good Luck,

Rob