Help me understand counter rotating props?
 

Fairly new to twin engines. I had a Larson with twin screws that turned opposite of each other. I now have a Sea Ray with twins, but both props are the same. Neither engine runs, so no idea if one is counter or not. If it were, I assume the outdrive would also be counter in order for the prop to work correctly. My question is this - is there such thing as a counter outdrive or is it just cabled backwards? If it is just a cabling change, what about the water pump - it is in the outdrive (Alpha) so wouldn't it be running backwards as well? Reason for all the questions is that I want to get a counter prop and make it like the Larson - the wake it left was awesome for skiing and I want both engines to turn "normal" as counter turn parts are more expensive and harder to find... It makes sense to me that for a counter rotating engine, you would only need to change the cam, starter and oil pump Maybe the dist gear is different as well. Then reverse the firing order or something like that... Just guessing...

Thanks!

Dustin

The drives are the same But wired backwards... Also it's the props that are angled backwards.... You prolly want them rotating inwards....hope this helps... Most people agree u should also swap the drives occassionally to make the gears wear more evenly. Kind of the same idea as rotating tires. Make sure and swap the props when you do this.

Thanks for the reply - so you are saying with my Alpha drives it doesn't matter the direction they spin, the pickup will work either way? All I have to do is find a counter prop and change the linkage? That would be too easy!

Alpha's have standard(RH) and counter rotating(LH) drives. They can't be run the opposite direction. The impeller is in the drive in an Alpha.

Bravo drives can be run either way.

crud. Now I wonder if the motor was counter as well as the outdrive (which would make absolutely no sense) but a marine engine guy told me it was common. Is there a way to tell by looking at the unit or do I have to find a number on it somewhere to tell if it is RH or LH?

And I got educated on something!.... Wasn't aware of that but then again I have only had bravos

as far as i know all stern drive engines are std rotation. i think they started making counter rotation alphas in the late eighties. so if your boat is older you may have two right hand units. usually the end of the prop shaft will be stamped with L, LH or Cr if its a counter unit.

Alpha and Bravo engines( pretty much all stern drives too)
rotate LH....the clutch's wont work when the input shaft
turns RH on alpha's and bravo's.

Rotation changes are all done in the drive

Not true, They only make Bravo's in standard rotation. The rotation is changed by changing this shifter cable on the shifter lever.

Griff explained it the best. He lives in Omaha also so he must know what he is talking about:drink:

I was addressing the question on ENGINE rotation.

Alpha's and Bravo's will not work when
the input shaft is turned R/H. ( opposite of normal)

The clutches operate in a one way fashion,
turning them backwards just makes them over run.

So to sum it up....

Alpha- only makes clockwise rotation drives. Therefore you could not. Swap these drives from side to side. Which in turn means alphas may not last as long and require rebuild sooner?

Bravos - make a drive that is capable of runnig clockwise and counter clockwise at high rpm's....what makes one rotate clockwise or counter clockwise is the connection to the shifter fork in the rear of the drive... They can be swapped from side to side. The props are also side specific.

This correct ???

Thank you everyone for your knowledge. From this I now know the guy that told me it is common to have a counter engine with a counter outdrive is full of BS. I also learned that you cannot just switch cables on an alpha and run it in reverse - I have to purchase a counter assy. Last, neither of my engines are counter rotation, phew! Now to find a unit and prop... A wise man once told me that BOAT stands for Bust Out Another Thousand and boy was he right!

They do make a counter rotation alpha,
it uses a special lower unit.

Bravo's, don't care.

Alpha's come in both RH and LH rotations now. Originally, I think they only had RH. On a lot of older Alpha twin engine boats, they had standard RH drives on both sides. They can be switched from side to side. They will still turning the same direction. Rebuild time is not a factor.

Bravo's can spin either way. If you spin it RH, it puts downward pressure on the upper gears. If you spin it LH, it puts upward pressure on the upper gears and top cap. They can be switched side to side. You can also change rotation by reversing the cable connections at the shifter and swapping props from side to side.