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Twin Alpha one Gen One

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gonflyn

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I recently posted a question about my 91 Wellcraft Monaco...Well...I thought it had Alpha one Gen 2, turns out they are Alpha One Gen ONE? Guess you can't always believe what your read...need to check things out.

So...anyway..now since I have a problem with the PORT Drive, I'm trying to find information on how the Twins work? I understand they are outboard turning props? Port turns counter clock wise, Starboard turns Clockwise. Is this a function of the engine or the out drive? Long story short....If I need to replace my Port Sterndrive, does it matter? Or will I have to order one specific to a Port drive engine?

Learning as I go!!!
 
It depends.
Only real easy way to tell is to see which way the engines spin.
If they both spin in the same rotation/direction then one drive will be a counter rotation lower unit on one drive. It is the lower half of the drive which is counter rotation.
I dont think with alpha out drives you would have a reverse rotation engine.
 
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I agree with Chris. Both of your engines will be Std LH Rotation.

(engine rotation is always viewed from the flywheel end)

faq-ro5.jpg




With a standard RH prop drive, the foward-most driven gear places the prop thrust against a large tapered roller bearing.
While reversing, the aft-most driven gear takes the more mild load.

With a reverse LH prop drive, the aft-most driven gear places the prop thrust against a differently designed thrust load bearing scenario.
While reversing, the foward-most driven gear easily takes the load.
 

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And thank God for that! I maintained a boat with a reverse rotator on the starboard side for years. Never again.

Jeff
 
I will add that the Merc A drive gears themselves don't know or care which direction that the prop is being rotated.
Who does care, are the thrust bearings.
In other words, if a std drive was used in Reverse..... in order to spin a LH propeller....., the components would likely fail.

With the Merc B drive or any Volvo Penta drive, we simply switch to the oposite transmission driven gear.
No change required to the lower unit gear set/bearings.



.
 
Hey, Thanks for all the good info!!! I guess I'll be taking it apart in a couple weeks when I get some time and see what failed....other than the fact the previous work done on it appears to have replaces the bell housing gasket with RTV??? I guess some people just need to save that $5.00 for more beer!!
 
Thanks for the info and diagrams. SO in real simple terms, Since both engines had a counter clockwise rotation, the "drive shaft" out of each engine turns the same direction. It will go thru the engine coupler, into the upper unit and the gearing there changes the rotation from horizontal to vertical down thru both the upper and lower units. It's in the lower unit, where depending where you position the gears to mess, it's going to turn the prop shaft either clockwise...or right hand, or counter clockwise, for the left hand. And, like you stated....the drive really doesn't care which direction it's rotating, that is determined by positioning the throttle/shift lever into forward or reverse. SO...in theory, with out changing any linkage for shifting, IF...I had two good drives, swapped the props...left to right and right to left forward thrust would still be accomplished, but my prop walk would be inward instead of outward...making it difficult to maneuver in tight spaces. If I put a standard drive on the port side and run the land hand prop, it will work as normal, but just wear out the thrust bearing faster, because the load would be opposite the standard rotation and put more stress on the bearing? Are these that a correct assumptions??
 
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