2 inboard Engines, LH rotation

J

jmas

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If both engines were same rotation,what would be results when underway?
Boat is 34'
WT. 12500 Lbs.
Just Curious.
 
I would guess a pull to one side with a list to go with it.
 
That can't be accurately answered without knowing whether the transmissions are "full-reversing" type, which can be set up to allow props to turn counter to each other in same gear.

A large % of Tw/I/B's these days are both standard rotation engines with LH and RH rotation props. I wish mine were, instead Of RH/LH engines.
 
quote:
Originally posted by Sandy

That can't be accurately answered without knowing whether the transmissions are "full-reversing" type, which can be set up to allow props to turn counter to each other in same gear.

A large % of Tw/I/B's these days are both standard rotation engines with LH and RH rotation props. I wish mine were, instead Of RH/LH engines.

Click to expand...

Sandy, Trans. are same rotation Velvit Drives. I am replacing Starboard engine,RH rotation, more $$ than LH rotation engines.
Might make sense to change tranny to Reversing type while engine is out.
 
Joe- If you change transmissions to a different, full-reversing model VD or say Hurth ZF to accommodate 2 LH engines , I suspect you will likely have to install different length propshaft.

As an alternative, you might check with VD , as I seem to recall in the past their website noted that even their very common 71C and heftier 72c series could be special-ordered with output rotation opposite of standard ( and that standard output depends on the gear ratio).
That would lead to believe perhaps your present RH engine's transmission...might ... be able to be modified to reverse output. But I don't see that note on the website now and I might well have been mistaken.

http://www.velvetdrive.com/supportm.html
 
Your transmission is a reversing type. You do have reverse, don't you? What you need to know is whether or not the transmission can run in reverse at full power indefinitely.

If the box can run backwards (and the ZF boxes in Meridians can)then it is a simple matter of changing the cable connections.

There is a very small difference in output speed because of the extra gear (about 2 to 4%) which is commonly ignored.
 
I had same rotation IO drives a few years ago. When backing into my slip it would pull to one side a little, I learned to compensate. . . .these were IO, not shaft drive.
 
My Silverton has twin standard rotation 454XLs. Transmissions are velvet drive series 5000. One transmission runs in reverse while the other is forward as suggested by rbmitchell.
 
quote:
Originally posted by Sandy

Joe- If you change transmissions to a different, full-reversing model VD or say Hurth ZF to accommodate 2 LH engines , I suspect you will likely have to install different length propshaft.

As an alternative, you might check with VD , as I seem to recall in the past their website noted that even their very common 71C and heftier 72c series could be special-ordered with output rotation opposite of standard ( and that standard output depends on the gear ratio).
That would lead to believe perhaps your present RH engine's transmission...might ... be able to be modified to reverse output. But I don't see that note on the website now and I might well have been mistaken.

http://www.velvetdrive.com/supportm.html

Click to expand...


You can install and run a 70 series velvet drive for either a rh or lh engine, but it must run in the same primary direction as the engine rotation. You can not use them to "reverse" the engine rotation. The 5000 series on the other hand you can reverse direction full time as a means of using two engines of the same rotation and use the transmission to reverse one of them.

However if you already have 71 series transmissions and thinking you can just install a 5000 series on the new engine to change rotation, realize that the 71 and 5000 series have different down angles and will significantly change the geometry of the engine relationship to running gear. Not an inexpensive swap.

For manufacturers that no longer produce reverse rotation engines, this can get to be a real pain. For new boats, it's easy to design for this. existing replacements of only one engine get interesting.

If the reverse rotation is available for a premium, just pay the extra fee. Bite your lip and do it, it will be cheaper than changing running gear. If you install two engines of the same rotation, you won't be able to fix it cheaply when you find out the handling is crap and will take a beating come sales time.

Many have been through this .
 
But PT boats had all 3 engines turning the same direction, right? How would three engines all turning in the same direction affect handling if Ghost is correct about handling being crap on two turning in the same direction?

V/R
 
Thanks all for great info.
Sounds like best bet is to spend the extra $$ for a RH rotation engine or have the problem engine fixed. If I go for 2 new engines in the future, Ill go for same LH rotation engines.

Problem engine sounds like connecting rod bearing knock, maybe not a hard fix.
 
quote:
Originally posted by williamabernathy

But PT boats had all 3 engines turning the same direction, right? How would three engines all turning in the same direction affect handling if Ghost is correct about handling being crap on two turning in the same direction?

V/R

Click to expand...


Bill, Are you sugesting putting a 3rd engine in the Boat?
 
Joe,
Shucks, that would be interesting, wouldn't it? No, I was just wondering about handling if two engines were turning in the same direction, and my mind wandered to remembering reading that PT boats' three engines turned in the same direction. Didn't mean to wander too far off topic.

V/R
Bill
 
To address the original question ( substituting "props" for "engines" ), I expect you might experience some torque-steer at speed so even with hydraulic steering the wheel would likely turn easier one way than the other , plus there might be some lean to port that could be addressed by trim tabs.

But low speed maneuvering , particularly backing, would likely be pretty biased to one side as the stern was pulled in F to the side of whichever "hand" props your transmission output requires, And opposite backing, of course. (Double the prop walk effect just a single engine boat would experience. ) I think I'd really want to avoid that situation after enjoying the great maneuverability of counter-rotating I/B props for so long.

The "pro" would be a spare prop could replace either side. :D
 
I am looking to change out my gears soon so that I can run two similar rotation engines and run one in reverse - this way if ever my stbd motor fails I can run power steering pump off other motor....today I am nearly dead in the water if Stbd fails
 
Footloose, the engines would turn the same direction, the reverse would be done with the transmission.
 
Joe, I think you have 454's in your boat right. Take a look at Promar engines out of New Jersey. I bought a 454 from them a couple of years ago for $2600 that included shipping on the old and new one, no core charge and 2 year warranty. The rebuilt they send looked like it was brand new and was perfect. Promar is a big professional engine builder and they can build you what ever you need, let/right, standard 330/350hp to race monsters.
Ask for Dave in marine engines, great guy most helpful, always willing to help out even after the check clears, ;-)
 
Joe in my Mainship both 8.1L HO's were the same rotation. The original engines had one counter rotating unit. I had new V drives installed one that was made to reverse it's input and it used a special idler gear.
It worked great.
Bill
 
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