transmission rotation

[H]

Hi Forum folks,
Who amongst you can sort out the right hand, left hand, rotation thing for transmissions?
I have a Chevy small block which rotates clockwise when looking at the front of the motor, or anticlockwise when looking from the prop end.
So do I need a left or right rotation, transmission and prop. :confused: :confused:
Regards “H”

[brad9798]

left, far as I know ...

[Gerald]

I believe it would depend upon what transmission you are talking about.
Gerald

[ion barnes]

You have not given a whole bunch to work with, but, the standard engine will rotate clockwise when viewed from the front. The transmisson can alter that if required to give counter rotating props by adding an extra gear set to change rotation. The transmisson is there to pimarily to increase torque and reduce engine speed to a limit suitable for the prop intended. Some engines dont turn fast enough or the props are sesigned for high speed and then the need for a trans is nil execpt to change direction.

[jwaldin]

All motors were originally designed to turn clockwise when viewed from the front. Why? Because that was the direction most people 'hand cranked' to start them. Why? Because most people are right handed.
Go to your local prop shop. They'll help you with the right prop for your engine according to its horsepower and torque and rpm.
Hope that helped a bit.

[John B]

It's the kind of thing you want to get right H. The probability is that you'll end up with a left hand prop. It seems that most petrol motors are left h and most diesels are rh. probably because of the gearset thing mentioned above. plenty of exceptions though. I read here that the people with twin motors ( petrol) even get one motor turning the opposite way to get counter rotating props rather than mess with the gearbox.
funny story: a friend of mine got some trouble with his gearbox one summer. big panic trying to get it fixed. It turned out that a previous owner had changed the motor to a diesel from petrol but didn't want to go to the expense of changing the prop. so he didn't. the problem with the box was that it had been run in reverse ( going forward)for 15 years... :D kind of stressed in places it wasn't supposed to be stressed.Amazing it lasted so long.

[nedL]

H, In 'marine applications terms' you have a left hand engine. - When you lok at a marine engine from the propeller end, clockwise rotation in forward is right hand. Counterclockwise rotation in forward is left hand. What you are describing is a left hand engine requiring a left hand prop. (I do not believe it is not normal to reverse engine rotation with the transmission. at least it wasn't up to about 15 years ago - have things changed since then(?))

[cbob]

H, First thing here what you are calling a transmission is called a reverse gear, or in the case of a reduction gear included or attached, a reverse reduction gear. In order to reverse the rotation on marine, read marinized gasoline and diesel industrial engines, the direction of rotation is determined as to which end of the block, the reverse, reverse reduction gear is attached, i.e. one is end for ended. Port and starboard engines, in twin engine installations turni in opposite directions, looking toward the propellers from astern, turning in a direction to move the boat forward, will rotate outwards at the top, like, port propeller counterclockwise (left rotation). Before smaller imported diesels, most single screw installations were right hand rotation, blade tips turning clockwise, viewed from astern. One advantage of this was the srern walking to port while in astern, assisting manuevering. On drives with no reduction, direct drive (1:1) the propeller and engine turn with the same rotation, some, planitary type reductions, turn in the same rotation as the engine, others may have a reduction gear setup which may reverse the engine direction of rotation, If a reduction gear is used, the mechanical details of the unit must be known prior to propeller selection. My gas engine, turning a prop right handed through a direct, planitary reverse gear box, cranks counterclockwise to start, looking aft at the flywheel. The type engine you propose, may not be suitable, partswise, for end for ending, so a reverse gear selection may be limited to one suitable, and in addition, a rduction (find out what ratio you will need first)gear may reverse direction also. Reverse gears are not designed for sustained operatioin reverse, so avoid an installartion, which requires the gear from being used in reverse to move the boat forward. Luck, cbob

[nedL]

Well said cbob. I probably should have made that 'transmission' vs. reverse gear' correction also. Keep in mind that end-for-ending the engine isn't the only way to reverse the rotation. A swap of the cam shaft will do it too.

[John E Hardiman]

Originally posted by nedL:
A swap of the cam shaft will do it too.Don't forget that that may require a new oil pump and pistons also.

[nedL]

Yes, there are some other things besides just the cam shaft. Of course one of the most important things to remember is to change the paint to the type labeled "for counter rotating use only". :D ;)