any one running a 23/ 25 cat with same rotating motors

[cave man]

wanted to see if any tried or runs a 23 25 ft cat with twin motors rotating the same way

[JOLLEY]

Not a good idea for high speed. If it gets up on the tail it will crab and try to swing out from under you. Slow speed app's can get away with it.................. Find a LH Lower and sell the other RH. Bill

[phillnjack]

Why not just simply put a left hand prop on and put in reverse ?.
the bearings would still be used in exactly the same way as normal so thrust would be no different to normal..
its what was allways done on Volvo penta drives to get counter rotation.

phill

[dompie99]

it could be done BUT it,s not the proper way to do it....the gears and not used on their ''power edge'' profile, look at the way the gears are ''molded', and you will understand.

[cave man]

hi jolley whats the 25 in your pic run what 250 are on it

[baja200merk]

Why not just simply put a left hand prop on and put in reverse ?.
the bearings would still be used in exactly the same way as normal so thrust would be no different to normal..
its what was allways done on Volvo penta drives to get counter rotation.

phill

Bravos do the same but the outboard cases will not survive. :nonod:

[BUZZIN' DOZEN]

I don't remember who, but several yrs. ago an offshore racing team by accident, put two like rotation props on their cat, as soon as they got on plane their day was over......:o

[phillnjack]

ive never noticed any difference in how the gears are cut at different angles, so in that case your saying revers is cut different. ?
well they should be cut the same as they both turn the same and both use the same power from the smaller gear in exactly the same way.
how are these cut different ? got to ask as this don't make sense.

the 3 gears are meshing all the time, so therefore the centre gear coming down is cut a certain way as will bother the 2 larger gears
as it will always be pushing the other 2 gears the same way, they don't change rotation, so I cant see why they would ever be cut differently.

it don't seem to make much sense that one of the gears would be cut differently, therefore buggering up the smaller drive gear all the time.

and why wouldn't a outboard case survive ?
for what reason would it break ?
its still doing exactly the same job just turning the shaft in the opposite direction no more and no less stress than normal.

I am just not understanding why it would be so difficult ?


phill

[PanRonnie]

it,s not so much that the gears are cut differently but the build/construction of the bearings
standard rotation the gear in the torpedo nose is engaged
counter rotation the one against the prop shaft carrier these have more bearings behind the gear wheel

[JOLLEY]

hi jolley whats the 25 in your pic run what 250 are on it


25 Ocean Express Kevlar with twin 250 Yammis. Mid 90's with 30x15 wheels. Love the boat. Used to be a race boat around the Great Lakes before I re-rigged it with Sparky at Vicious Marine...... Thanks for asking, Built in Algonac, Mi.

[powerabout]

ive never noticed any difference in how the gears are cut at different angles, so in that case your saying revers is cut different. ?
well they should be cut the same as they both turn the same and both use the same power from the smaller gear in exactly the same way.
how are these cut different ? got to ask as this don't make sense.

the 3 gears are meshing all the time, so therefore the centre gear coming down is cut a certain way as will bother the 2 larger gears
as it will always be pushing the other 2 gears the same way, they don't change rotation, so I cant see why they would ever be cut differently.

it don't seem to make much sense that one of the gears would be cut differently, therefore buggering up the smaller drive gear all the time.

and why wouldn't a outboard case survive ?
for what reason would it break ?
its still doing exactly the same job just turning the shaft in the opposite direction no more and no less stress than normal.

I am just not understanding why it would be so difficult ?


phill
Take one apart and you will learn.
For starters the prop shaft rotates with fwd in rh box.
In lh it will be going the opposite direction yet it still has to take all the thrust while sitting on fwd and going the opposite direction.
Volvo sd has the gearshift in the top box like a bravo (and every other top box shifted stendrive) its dead simple Doh!
Thats why many lh outbosrds were built with lh powehead so the gearbox worked simply, but with opposite spiral gears of course.

[Dave S]

If ya run a RH in r it will mean the prop thrust is going the other way than the front gear.... 7000 rpm of weld........Merc made 2 cases.... a locker that has no front gear,just a spacer that holds the shifter dog in place to the back gear and puts the thrust to the front bearing. Or the shifter case that puts the thrust to a special bearing behind the Rear gear so the gears and shift dog a thrust free.......Hope that helps......

[powerabout]

Only successful way for an outboard is to run a lh powerhead( but gears have to suit thst)

[cave man]

that gives me hope with my project just put 2 200 Johnsons

[phillnjack]

quote
For starters the prop shaft rotates with fwd in rh box.
In lh it will be going the opposite direction yet it still has to take all the thrust while sitting on fwd and going the opposite direction.
Volvo sd has the gearshift in the top box like a bravo (and every other top box shifted stendrive) its dead simple Doh!
Thats why many lh outbosrds were built with lh powehead so the gearbox worked simply, but with opposite spiral gears of course. "

I was not talking about sd, I was referring to the Volvo 290sp outdrive.
Now no matter what way round the shaft is turning it should still be held in its bearings and thrust washers taking the brunt.
the forward and reverse gears should never have pressure put on them, todays engineering makes sure gears do not fit like that and that's what
thrust bearings and shims are all about.
so by saying sitting on forward gear is wrong as it would be no different to what its doing right now as in gap to gear if correctly shimmed !!!

that's how I see it . maybe its a thing with newer engines ?
its not like when on a moving shaft and the actual gears move to change gear, both the forward and reverse are being used all the time.

i just looked at a set of forward and reverse gears on an outboard prop shaft and I cant see any difference in how the gears are cut, they
look identical to me, but I only have a normal magnifying glass not a microscope. ( omc triple 60hp gear set, not big engine).

will take your word for it that the bigger ones are cut differently, will be getting a look at some soon down the boat shop.

phill

[phillnjack]

Dave s wrote
If ya run a RH in r it will mean the prop thrust is going the other way than the front gear.... 7000 rpm of weld

who said anything about reversing the boat at 7,000rpm ? the propshaft thrust will still be going forward if using a left hand prop.
now that is obvious, so the thrust is still taken up on exactly the same thrust bearing and shims.
and what about counter rotation gearboxes where the forward gear is nearer the prop instead of nearer the front of gearbox ?
this is no different to what I am saying.


phill.

[powerabout]

Dave s wrote
If ya run a RH in r it will mean the prop thrust is going the other way than the front gear.... 7000 rpm of weld

who said anything about reversing the boat at 7,000rpm ? the propshaft thrust will still be going forward if using a left hand prop.
now that is obvious, so the thrust is still taken up on exactly the same thrust bearing and shims.
and what about counter rotation gearboxes where the forward gear is nearer the prop instead of nearer the front of gearbox ?
this is no different to what I am saying.


phill.
geez
you really need to get all those 70 parts in your hand to see how a gearbox works

[Scotth944]

Nope mines cr and spins in

[phillnjack]

I have the gears and shaft right in front of me. I see no reason for it not to work.
It does not matter if the gear is at front or back as there should be a slight gap at all times if shimmed correctly.
From what your all saying is that if you used reverse as much as forward the gearbox
Would fail !!!. That is rubbish. Many large outboards are used on pusher barges in europe
They do almost as much work in reverse as forward and dont have major gear failures.

[powerabout]

When the box is in reverse the prop is pulling the shaft out of the box andits sitting on reverse gear that is turning with it
Your saying run it in reverse with lh prop so now the thrust is going into forward gear but its going the otherway and you have the parts in your hand is there a bearing to stop the 7000 rpm spin welding happening..NO
Try it on your engine and see what happens.

[Raceman]

I have the gears and shaft right in front of me. I see no reason for it not to work.
It does not matter if the gear is at front or back as there should be a slight gap at all times if shimmed correctly.
From what your all saying is that if you used reverse as much as forward the gearbox
Would fail !!!. That is rubbish. Many large outboards are used on pusher barges in europe
They do almost as much work in reverse as forward and dont have major gear failures.

What these guys are trying to tell you is 100% correct and a Right gearcase run in reverse under full power will destroy itself almost very quickly. I don't know what parts you have in front of you, but I doubt they're from a V6 Merc or you should be able to see why. It has nothing to do with shimmed correctly, but where the thrust load is under load, and the reference to welded at 7000 RPM had nothing to do with shifting at 7000 as you replied, but rather where the load is at full RPM. The rotation of a right gearcase uses the front gear in the case to go forward. A lefty drives forward with the rear gear. Since the tendency of the gear is to move away from the pinion under load there must be a surface other than the way the Merc righty case is made. You may also be confusing yourself that you are reversing the rotation of the driveshaft (input shaft) however it is still turning to the right. If you try to reverse the rotation of the powerhead to make the propshaft rotate lefty on a righty gearcase, then the load would be against the front as required.

EDIT: Powerabout, you're a lot faster typist than I am. When I started typing your post wasn't up yet.

[powerabout]

they are all the same Raceman, just a thrust washer between the propshaft and forward gear from about 40hp and up on anything.

[phillnjack]

can nobody here see that the gearbox is not in reverse at all ? the prop would not be trying to pull the shaft out the back of the gearbox, its still going forward.
the gears are never being reversed, they are allways going the same way as per normal .

The engine is turning the the main shaft in the exact same way all the time .... correct
the gears are turning the exact same way all the time .... correct
the thrust bearing in forward part of the gearbox is taking the forward thrust exactly the same as per normal....correct
the spacing between gears is exactly the same as per normal.....correct

the gear casing plays no different part in this operation than normal..... correct.

now we come to the clutch dog that simply goes forward and backwards to engage the gears to the PROPSHAFT....correct
this is the only part that actually changes direction , but with a left handed prop the thrust is still going forward and not backwards,...correct

under normal use none of the gears are being pressed against the main shaft gear by force, and neither would they be when the left handed prop is used...correct

so where is the problem that would cause a problem to the gear casing ? there isn't one.

BUT this is only if using a left handed propeller, as we are not talking about running a thousand hours at 7,000 rpm backwards.

the rotation of propshaft is only changed by the forward pr backwards movement of the clutch dog.
it has nothing at all to do with the gears or bearings as they are all still running in the exact same direction as per normal.


lets just say for arguments sake that normally we chuck the engine into forward gear and the thrust from the propeller moves the
propshaft forward into the gearbox 1/100th of an inch with a right hand prop.
Now if we put the gearbox into what we call reverse and use a left handed propeller it would still be the same as in 1/100th of an inch movement forward of propshaft.
so the bearings thrust washers gears mainshaft you name it all still take the exact same strain.

I am presuming that all three gears in the big mercs are at a constant mesh exactly the same as in a triple omc and 4 cylinder inline merc etc?

here is a cutaway of a verado showing exactly what I am talking about.

http://www.youtube.com/watch?v=MvA3SYrQJyI&amp



phill

[Raceman]

can nobody here see that the gearbox is not in reverse at all ? the prop would not be trying to pull the shaft out the back of the gearbox, its still going forward.
the gears are never being reversed, they are allways going the same way as per normal .



Since you obviously know so much more about this than any of the people here who have tried to explain to you why it will not work, please do this with your own Merc gearcase, preferably a brand new one so you can experience the explosion of brand new stuff and get back with us on the results. You should also contact the engineers at Mercury Marine and explain to them why there's no reason to build a reverse rotation gearcase. I'm sure they would welcome your input since it would obviously save mega bucks in engineering and manufacturing costs.

[phillnjack]

well raceman your such an expert why don't you go tell Suzuki it don't work too !!!!

go check out their DF300AP/DF250AP, they do exactly what I am talking about, no changing gearbox they use the exact same stuff in either direction.

they also have same amount of gears as a verado in the bottom and go both way no problems at all.



phill

[Chaz]

Phil ,
I like hard headed people , they remind me of me .. ;)

In theory , you are correct. In application , you run into problems.

The backlash setting is twice as loose for reverse as it is in forward . Don't know what would happen, since I cant really think of anyone who really runs their $hiz very hard in reverse.

But more importantly, Pan , showed you the difference in the exploded view back on post #9
The right is on the left , and the left is on the right ... :eek:

See part # 28 , those two little half moon clips . They , along with the help of 25 , 26 and 27 locate the lefty's propshaft position within the carrier adapter #23 and the carrier #30 . The carrier alone can not deal with the load placed apon it , by itself .. :nonod:

7000 rpm neutral drops .. reminds me of when I wuz 15, id borrow my moms 455 Pontiac to go on a ... ahemmm ... job interview .. :eek: :eek: ;)
Gotta love them Turbo 400 's .. :thumbsup:

http://www.screamandfly.com/attachment.php?attachmentid=299751&d=1402674573

[HarleyPHD]

My 150 mercury has an large tapered roller bearing for the forward ring gear, but a ball bearing for the reverse ring gear. When the ring and pinion gears are under load they are trying to push away from each other. The tapered roller bearing can take side loads better then a ball bearing.

[Raceman]

well raceman your such an expert why don't you go tell Suzuki it don't work too !!!!

go check out their DF300AP/DF250AP, they do exactly what I am talking about, no changing gearbox they use the exact same stuff in either direction.

they also have same amount of gears as a verado in the bottom and go both way no problems at all.



phill

Now you're just acting stupid for the sake of arguing. Nobody has said it can't be done, but a Merc V6 gearcase won't live that way because of the way it's built. A Merc Bravo case will live that way because of the way it's built. I don't have a clue how Suzuki builds theirs and don't care. I also don't know how Verdados are made and don't care. Was there any mention of Suzukis or Verados in the original question? Maybe a 1947 Elgin or a Scott Attwater case will also live under the conditions you are clinging to, but a Merc V6 will not. A Merc inline case also will not. The prop pushing forward as you mention has nothing to do with the loads we're trying to get through to you, but you're not paying attention regardless of how many people say it. The gears are trying to get away from the pinion that is driving them. When the rear gear is the driving gear it is pushing rearward. It is loaded against the bearing carrier. Prop does not matter. The load from the rear gear trying to move away from the pinion is going toward the bearing carrier and unloading the bearing in the forward gear. The Merc V6 gearcase and Merc inline case is not built to bear this load under full power long term conditions and will not live.

[tunnelfun]

Caveman Look at it this way.If twin counter motors put half as much load on the steering as a single motor you are about to put twice as much load on your steering as a single motor would put on your steering.Have you ever driven an elevated single outboard?Don't let anybody ride in the boat with you.I'm just saying.

[phillnjack]

No your the one acting stupid , original post did NOT mention any brand so stop trying to be pedantic.

[MercNuts]

No your the one acting stupid , original post did NOT mention any brand so stop trying to be pedantic.

Numbnuts it wont werc with a Merc. That means that with a majority of outboards that someone would run on a twin engine tunnel it won't work. If anyone is being pedantic it's you. The chances of this question being asked by someone planning on running a pair of Suzukis on a high perf tunnel is less than one in a million. Learn what you're talking about before you pick a fight and maybe you won't look like the idiot you've shown yourself to be now. Does it strike you that nobody else has chimed in and said hey thats a good idea.

[phillnjack]

well mercnuts
i will not get into a fight with someone from Alabama.:nonod:
i was bought up never to pick on or to even attempt to argue with someone who is not the full shilling.:p
i know you would love to sit and make silly noises and have a hysterical giggle with all your kin folk folk round
a fire singing ol Susanna and playing the banjo's etc:thumbsup:
so i will not go upsetting you and will not even bite, it just don't work this time Jethro.


now i am out of here as its too hard trying to get through,
i will leave you all to get on with your way of thinking on this subject.

im off to watch Ghanna win their game tonight . :eek:


phill

[MercNuts]

well mercnuts
i will not get into a fight with someone from Alabama.:nonod:
i was bought up never to pick on or to even attempt to argue with someone who is not the full shilling.:p
i know you would love to sit and make silly noises and have a hysterical giggle with all your kin folk folk round
a fire singing ol Susanna and playing the banjo's etc:thumbsup:
so i will not go upsetting you and will not even bite, it just don't work this time Jethro.


now i am out of here as its too hard trying to get through,
i will leave you all to get on with your way of thinking on this subject.

im off to watch Ghanna win their game tonight . :eek:


phill

Yeah, yeah weve heard it all. The governors mansion here burned all the way to the axles, the way you know that the toothbrush was invented in Alabama was because anywhere else and it wouldve been called a teeth brush and many more. But the truth is, youve labeled yourself as a moron to anybody that has ever been inside a Mercury gearcase of either the old inline or later V6 variety and instead of saying, oh I see, you continue hang onto your ignorance and argue. And we wish the best of luck to whoever Ghanna is playing at whatever sport that is.

[powerabout]

Yep alabama, the worlds largest market for outboard motors yet nobody knows anything about them, hard to believe really...
Well at least in the uk you have all the seagul outboard specialists to help you.the Seagul of course is about the technology level your mechanical skills would be comfortable with it seems?

[Euroski]

Only one way to settle this... do it and let us know the results

[cave man]

right now both motors are turning the same way. I am going to a least take it for a blast an see what dose ill let you guys know how I make out

[perfmarine1]

It will run ok. I will crab at higher speeds,and won't be as efficient as counter rotating. But it will work just fine as a pleasure boat. Been running mine like that for years.

[powerabout]

if you haven't had the pleasure of a lefty on a twin rig you dont know what your missing is one way to describe it...

PS What type of cat is that Perfmarine1?

[perfmarine1]

Eliminator Daytona 23' And I know what I will be missing.$$$$$$$$$$$$ Gearcase= $800-$4000 and hard to find for my motors. Prop= $600-$1200 Or merc motors $20,000-$40,000 Just not worth it for a boat I only use 3 times a year. Have 4 other boats to run and take care of.

[powerabout]

Yep
One day we will have a reliable omc lh box

[NZ Sidewinder]

When you run a right hand gearbox in reverse to act as counter rotating the consideration often overlooked is the load on the reverse gear caused by the pinion.
The more load that is applied to the pinion / reverse gear mesh, the more they try and push apart.
In forward gear this load is resisted by the pinion bearing on the drive shaft and the forward gear bearing.
When running hard in reverse, this load is resisted by the pinion bearing and the single row deep groove reverse bearing.
That revers gear setup isn't designed to take massive loads.

[powerabout]

When you run a right hand gearbox in reverse to act as counter rotating the consideration often overlooked is the load on the reverse gear caused by the pinion.
The more load that is applied to the pinion / reverse gear mesh, the more they try and push apart.
In forward gear this load is resisted by the pinion bearing on the drive shaft and the forward gear bearing.
When running hard in reverse, this load is resisted by the pinion bearing and the single row deep groove reverse bearing.
That revers gear setup isn't designed to take massive loads.
Dont forget you could have straight cut gears, Merc spiral bevel or OMC ones cut in the reverse direction..

[NZ Sidewinder]

I'm thinking that no matter what the tooth form is, when the reverse gear is loaded, the gear is trying g to move away from the pinion.
The reverse bearing isn't designed to tolerate that.
That reverse gear is being point loaded in that the gear is trying to tip over.
I know a bloke who purchaced a boat that was running a right hand box in reverse with a lefty prop and it was going but I wouldnt run it like that

[powerabout]

I'm thinking that no matter what the tooth form is, when the reverse gear is loaded, the gear is trying g to move away from the pinion.
The reverse bearing isn't designed to tolerate that.
That reverse gear is being point loaded in that the gear is trying to tip over.
I know a bloke who purchaced a boat that was running a right hand box in reverse with a lefty prop and it was going but I wouldnt run it like that
You would think but look at the tooth cut and the pinion thrust bearings, old Merc pulling in, old omc pushing out
Merc then changed to pushing out then said ok why dont we just hold it still..finally.

[NICE PAIR]

Running your Sportmaster units in reverse with the wrong props will cost you some $$ If you run it long enough, it'll cost you lots of $$$$ (I know a guy that did just that) ;)

[25two.stroke]

LH cases can be built to run 100% in both directions, just shim them correctly...its the RH that cannot be run hard in reverse as mentioned above.

The fact about Bravos running both directions is irrelevant for 2 reasons: Bravo lowers don't shift and Bravo lowers do not have spiral cut gears.

[NICE PAIR]

Is that because of the way the lefty handles forward propshaft thrust? Asking for a friend. ;)

[powerabout]

Is that because of the way the lefty handles forward propshaft thrust? Asking for a friend. ;)
you got it

[25two.stroke]

Is that because of the way the lefty handles forward propshaft thrust? Asking for a friend. ;)

How it handles propshaft thrust in both directions with those expensive ass radial roller bearings. $850 each or some nonsense!