In what's cases would a engine not be a standard rotation.

Inboards generally

I understand that. I know none of your high performance stuff is that way. Is it like stock style stuff ?

totally accurate

counter rotating motors were used in twin engine powerboats when attached to an alpha one drive, since you can't change the rotation of the drive. It sounds crazy, but Ive seen it in an older 240 Baja with a pair of small blocks, one motor spun backwards to drive the counter rotating alpha one.

I don't think its as common now, except with inboards. not many powerboats running alpha one's

Some Goofy people on the other side of the Hemisphere change their engine rotation to Counter react the torque of the rotation of their Heads when they flush them.

But that Guy is a Whole Nother Story

In my bigyellowcat I had two twin turbo 632 cuin bbc with one spinning clock wise and the other counter clockwise. I had straight arnesons with no gear box. And I had no transmissions or gear boxes ect. To change the rotation so I had to change the engine rotation. On the back of the engine there was an adapter that bolted to the crank where the flywheel bolts that had the spicer 1550 unjoint flange on it and the driveshaft straight to the arnesons input.

the engine does not really care which way it spins, at first we did not change anything but cam and distributor gear. After we blew them up a few times we ended up with a custom crank with the knife edge the opposite way but that would really not make a difference anyway. The biggest problem I had was there was only one company making a distributor gear that was counter rotating and it was made out of junk material and would only last an hour or so.

Actually only the very early alpha drives were right hand only. The first and only year that Alphas we’re hooked to 454big blocks was 1987, I had A Scarab that I bought new with twin right hand 454 big blocks. The boat handled horribly with the two RH drives crabbing and twisting left to right as the throttle was moved. After blowing the first or 2nd set of drives Merc furnished at no charge a left hand Alpha that used near net gears and they rebuilt the right hand drive with near net parts also, the twin counter rotating alphas were used for another year or two on small block applications.

this is interesting, i have a buddy that had an ‘87 or ‘88 Baja 240 with twin 350’s tears ago. There must have been a short time Mercury only made reverse turning alphas to go with a counter rotating engine.It seems like he had a hard time finding a replacement drive for it at one time, or I’m getting to old and my memory stinks 😂😂