Looking for some real out of the box thinking....
 

So here is the scenario. I have an 84 scarab with TRS's and I have a set of kaama drives that I really really want to put on the boat. My issue is that I am having no luck finding twin disc transmissions (without spending a fortune) so I am wondering if there are any other options? This is where the out of the box thinking comes in. I am not afraid of having to engineer something that works. Believe me I am far from one of those guys that needs everything to bolt up like a factory install or it can't be done. Unfortunately I don't know enough about the different types of transmissions out there that could maybe be retrofitted into a boat. I know the twin disc are unique in the fact that they can run full power in either direction. I can't imagine that this is the only transmission capable of this?

Anybody have any ideas?

Remember "out of the box thinking is what I am looking for"!

Thanks in advance!

Jim

Powerglides?

Don't know a lot about them other then they are still popular in mud trucks and race cars. I am not sure you can put full power to the reverse? Maybe the reverse is a different ratio also?

The 72's have been beefed up to handle some girthy hp loads ,flip the pump cover for different rotation needs ,cheap enough you could prob keep a spare in boat somewhere .b&m made some.mini trans like the blactrac back in day outside that its lenco ,ect .should be a interesting project

Are you saying you can flip the pump and the transmission will run in the opposite direction? Can you run full power like that?

The pump direction on 72s is determined by motor rotation, the counter rotation is in the gear reduction not the pump.

When a 72 is used on a counter rotating engine you need to flip the pump. What you need is a drop box reduction gear. I believe there were some made for velvet drives. Also look into the Walter machine company. They make the most compact vee drives and drop boxes I've seen.

Brain fart my end ,flip pump for opposite rotation engines .unusual in BBC world .yea if you need gear reduction and low drive centerline its going to be more difficult .may need to flip motors around and have a v drive surface drive scarab .would definetly be outside the box .

I will be replacing a pair of Twin Discs mg502 1.5 to 1 ratio with new ZFs sometime after the first of the year. I don't know what they are worth, but if you are interested I would part with them.

They work fine, except under hard throttle they will slip. The issue did not appear until I replaced the 415hp BBC engines with 500hp BBC engines. My boat weighs over 18,000lbs when loaded. I'm guessing there would be no issue in a lighter boat. I have been running it like this for over 150 hours with out any other problems, just have to be careful not to horse it on plane. This boat is a 42' Sport Fish with Arnesons.

Let me know

Steve

Velvet drive?

got my curiosity up, ZF Hurth and Paragon(?) Wow, they are proud of those! Velvet drives on Ebay could be had under $1k. I thought I paid to much for my other complete setup, looks like a hell of a deal now!

There are BW 72C's out there. You just gotta look. Any good trans shop can rebuild them.

Wannabe

I'm pretty sure Kaama drives are straight thru. If thats the case, then a down angle trans would work the best, such as the Twin Disc.

Those zf twin discs are some fancy little units .can't speak from experience , but looks like you will have to flip the motors around and go v drive to get the output shafts low enough then you have to figure out adapting the gear ratio to match available surface drive props .be a neat engineering feat if it could be pulled off

Twin discs come in fork lifts right? Maybe scrap out a couple of those.

Just now realized there is a guy I know in town that may have these or some hurth variants I am going to his place soon anyway for some v drive stuff ,going to take lots and lots of pictures .I do remember seeing a pair of counter rotating 426's there as well as big yanmar diesels

Twin Disc does have a modern replacement for the 502. I don't know the model off hand but if it's newer and more common might be a little cheaper? I do know it has more power/ rpm capacity and would actually be the way to go if you wanted original type components setup. One of the other more common names in marine transmissions also came out with a model with a lower output shaft height but I forget who it is and don't know how compatible it would be. Dan M. at Archer had crash boxes for them once upon a time. He might be a good person to ask about your plan. Edit- I had my 502's rebuilt by a Twin Disc dealer and it was so expensive you probably wouldn't believe me, so I understand why everyone wants a fortune for them.

Forgot about having to reverse rotation on one side

can you explain your comment? Did you mean "Forget about reversing a 72C" because they cant do that or did you mean "forget about having to reverse direction because its not necessary"? If the later is what you meant lets hear why? I actually asked this question a while ago (http://www.offshoreonly.com/forums/d...direction.html) and pretty much most people said the boat would pull really hard to one side.....

i would think you would want counter rotating props. what they mean is borgs have to be in forward. forward has to be turned the other way for opposite rotation with a borg. you must have an opposite rotation engine for that. and performance cams for opposite rotating engines are less common. also it doesn't get you down as deep in the hull as you want to be.

Your going to have to go with a extreme engine angle or find a twin disc and use a Borg liberty or hurth on the other side then there is the v drive mod , do you know what the kammas want for a ratio in and out ? Is it 1-1 ? Will it pull and do the proper rooster with a lh and rt hand prop set up if made to work ? I have a Trs boat at shop ,its a single with a zz502 ,but with a serp belt and custom pan it looks like it could go forward and down enough to clear a 18" trans ,take the spicers out of the rear of the kamma and swap.with v drive drag style cv joint coupler .
That's all the outside the box I have tonite but potentially way cheaper than scrounging up 14 grand worth of trannys that could still break and won't be getting fixed by Joe transmission

If whatever you have for motors is flat tappet ,rev BBC cams profiles still out there and cam grinders seem to be hungry these days in this area.

Thank you everybody for the true out of the box thinking! I just secured a pair of twin disc transmissions so I no longer have to find a way to work around this issue!

Good news is this still won't be a simple bolt in install. I plan to engineer a custom engine/transmission chassis that will make it even easier to install and remove my already simple engine setup!

I love customizing! :)

[QUOTE=502ss;4215480]can you explain your comment? Did you mean "Forget about reversing a 72C" because they cant do that or did you mean "forget about having to reverse direction because its not necessary"? If the later is what you meant lets hear why? I actually asked this question a while ago ([url]http://www.offshoreonly.com/forums/drives
I meant I overlooked the fact you had to reverse rotation. Because with my powerglide suggestion Im assuming they can not hold as much power in reverse as in forward. But maybe they can be built that way.
Anyway, moot at this point.

Hi Jim,

What did you have top pay for the Twin Discs, and what condition were they in? I would like an idea od value for mine that I will be selling.

Thanks,

Steve