Counter rotating engines or counter rotating props?

[Windjammer]

We're looking to move up to something 32'-34' with v drives. Just out of curiosity, are inboards really counter rotating or is rotation accomplished by flipping one of the transmissions (i.e runs in reverse)? In the case of flipping I could see this IF the gear ratios are identical for both forward and reverse? With any variation in gear rations, wouldn't this create adventures trying to sync the engines underway? Would you need to have different size props on each shaft?
Which way does Sea Ray go with the Mercruisers - rotating engines or flipping transmissions.
I'm interested in model years 2000 - 2003 covering the 5.7 MAG MPI, 7.4 EFI/MPI, and 8.1's.

Thanks

 

[Hampton]

I checked the other day. When I push both shifters forward, the port transmission lever throws forward, and the stbd throws aft. The rigging must be at the shift levers. I'm pretty sure my stbd transmission runs in reverse. Either way, one does. The props are slightly different sizes from the factory.

 

[sr360aft]

The answer is yes to both of your questions, in some cases the engines run in different directions, in others the transmission changes the spin

 

[fwebster]

When engines became controlled by electronics and ECM's General Motors stopped selling counter-rotating engines. If you find an early boat you may see one with counte-rotating motors, but it is getting harder and harder to get replacement engines that counter-rotate.

Most later engine/transmission packages....like after 1995....achieve counter-rotation by running on transmission in reverse and one in forward, as John says.

There is usually a slight difference in ratios in forward and reverse, but it is a fraction of a percent and not enough to tell or feel it and certainly not enough to affect the ability to synchronize the engines under way.