Engine rotaiton

[coolair]

I was able to search the forum thanks to the hard work of a couple guys! (thank you again) but couldn't really find an answer.
I am starting to 2nd guess my self on which engine goes where.

Port engine - is the standard rotation engine - from the flywheel it is CCW and thus needs a left hand prop.
Starboard engine - Is reverse rotation engine - from the flywheel it is CW and thus needs a right hand prop.

If I screwed up and mounted them backwards, what effect would just switching the props have?

[Tony Meola]

Matt I cheated and took this off the internet


What rotation engine do I have?

Engine rotation is viewed from the flywheel of the engine, clockwise would be Right Hand, and counter-clockwise would be Left Hand.
FLYWHEEL
TURNS COUNTER-CLOCKWISE

FLYWHEEL TURNS CLOCKWISE

LEFT HAND
ENGINE ROTATION
RIGHT HAND
ENGINE ROTATION
Since you usually cannot see the flywheel with the engine in the boat it can also be determined from the front of the engine. If you are looking at the front of the engine at the belts and pulleys, clockwise would be Left Hand, and counter-clockwise would be Right Hand. Never rely on propeller rotation to determine engine rotation. ALL I/O ENGINES ARE LEFT HAND!
BELTS & PULLEYS TURN CLOCKWISE

BELTS & PULLEYS
TURN COUNTER-CLOCKWISE

LEFT HAND
ENGINE ROTATION
RIGHT HAND
ENGINE ROTATION

Another subject that seems to puzzle people not familiar with marine engines is engine rotation. I am not talking prop rotation here, but the actual direction that the engine turns. The reason for the confusion is, on older marine engines, when you go shopping for parts they ask you, what is the engine rotation? The direction it rotates determines the part you get.
Most marine engines are left hand rotation, also known as standard rotation. But, left hand from what view point? The usual way of looking at this is to use the flywheel to determine rotation. If you look at the engine from the end with the flywheel and the flywheel turns counterclockwise, or left at the top, it is a left hand rotation. If it turns right, or clockwise it is right hand, or reverse rotation.
But most people don’t look at the flywheel end of the engine. They see the end with all the pulleys and belts. So at that end you would reverse the above. If the engine appears to turn clockwise at the pulleys, it is left hand or standard rotation. If it appears to turn counterclockwise at the pulleys it is right hand or reverse rotation.
However, in this age of fuel injected engines, and the use of mostly truck blocks for marine engines, all of them are standard rotation. They are all left hand rotation.
At the prop it is another matter. If the boat has a single engine, then the prop usually turns the other way, to counter the torque of the engine. This is done with a transmission, or what in the marine world is called a reduction gear, that changes the rotation to right hand at the prop. If you have twin engines then counter-rotating props are used. That is, one prop turns to the right, the other turns to the left. Usually the starboard (right) prop is the right hand prop, and the port (left) prop is the left hand prop. This is done to improve maneuverability and make the boat go in a straight line. Occasionally a designer will reverse this, so check your boat to see which way they turn.

[scenarioL113]

You have gasoline engines I assume, correct?

Hypothetically if you installed the engines incorrectly you could have a few options

I have to ask what transmissions you have? Velvet drives are designed to run left or right but need to be set up to do it. Velvet drives CAN NOT run in full power in "reverse". This is why they can be setup to run the input shaft in either direction. The output shaft can not run on full power in "reverse" or also known as "opposite" direction of the input shaft.

ZF and a few other transmissions are designed to run either way. I mean they do not have a forward or reverse. They can run either way with full power. They are able to run full power opposite the rotation of the input shaft.

ZF etc are ideal for Diesel engines for this reason. As far as I know diesel are not able to run opposite rotation. I think it would not be possible bc of the fuel delivery system etc...

If you have NON Velvet drives, I think you would just be able to reverse the linkage on your transmission cables and run the transmissions the opposite way and have your left hand prop on port and right hand on starboard.

It gets totally confusing and I may not even be making sense but I went thru this yrs ago on my diesel conversion and got ZF Tans for this very reason. I had to get rid of my old velvet drives bc they would not work for the diesels.

[coolair]

I have gas engines and velvet drives. I know the transmissions are mounted to the correct engines and the pumps are correct.
If what I am ready from Tony is correct then I think I am OK. I think I just over thinking it.

[Tony Meola]

Matt

If you have the engine rotation reversed then instead of turning outboard the props will turn Inboard. When put in gear, the starboard prop turns outboard forcing the stern to port and the if the Port is put in gear it pushes the stern to starboard. That helps in how the boat handles and steers.

Prop turning in on the starboard side would want to push the stern to Starboard and of course the opposite on the Port engine. Changes the way the boat handles and turns.