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.

[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......

[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]

[QUOTEit runs oppositephillnin fowardack;2648351]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[/QUOTE]
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