Borg Warner 71C Limitations
 

Was surprised to find from someone here that the 71C has a 300 HP rating. My boat had 500HPs before I repowered it with 420s so who knows how these things survived.

I dont know how a trans works so humor me:

1) if I feed it too much HP what happens?
2) Does it overheat or parts break or it slips?
3) What symptoms would I see?


If I decide to upgrade (since I could frankly use more reduction and I want to add more HP with small blowers - what straight (no down angle) trans could I use? I'm hoping not to have to move the motors or redo the drive shafts.

Thanks!

You need at least a 72C just because it handled whatever power dosen't mean it wil keep doing so. I believe the unit you need is a 10-18 Model 72 that has bigger internals and the biggest difference is in the size of the planetary gears.
I have some transmissions including a 72 but am unsure if you can use your tailstock with it. BBB

I also believe the 72c is a wee bit longer so you would have to move the engines fwd I believe about 3/4" to 1".

John:D

Thanks guys - the current set up has a 1" spacer between the trans and the drive shaft so I might be okay without moving the motors. The 72C can handle 450hp I think per the spec sheet.

Can it beefed up a bit somehow/somewhere if I want to run another 100 HP though it?

Can it run in both directions (one counter rotating motor) or is it two different models I need?

Yes it can run in both directions...You have to index the pump. With the tranny removed the pump is in front.

You can also beef these up to handle more horsepower. There are a number of people around that can do that. Just do a search on here for transmissions and I am sure a few will come up.

John:D

Try Paul at Long Island Marine Transmission. We had him do the trannys for the 38 KV Scarab with 588's and Konrads.
No problems whatsoever !
He also did the 72 V Drive in Joe Pepitones boat, retired Ny yankee 1958-1973. I worked on the boat and fixed one of his 454's.
I'll try to find his # I looked in my books, I' have to look more. BBB

thanks guys
I'm in S E Florida if that helps

send them to bam.

http://go-fast.com

Huber transmissions (http://www.hubermarine.com)will set up your 71c's if you have them. (Now the Transmissions are being done by Earl Zimmerman) He can add more clutch plates. He can build them to Huber 925's. They will hold quite a bit of HP. Of course the 72's are superior.

http://texomamarinegear.com/
Also Texoma Marine Gear, Kendal can get you taken care of.

Great turn around time.

You could stay with the 71's if you expect 500-600HP. They can handle this by adding two more clutch plates. I raced 8 years with this set-up with 500-525HP...never touched them again. BAM would be a safe choice for the upgrade. Mercury used the 71's (red tag) with the 370 TRS package.

BAM is the best and in your area. Quick turn around too.

That's right. Go to Marc at Bam. They have a one of a kind transmission dyno and are the experts...
The 72 has bigger internals and may consume more HP to run. But is an excellent piece.
You could do all kinds of things including installing brass tank clutch plates, even if you warp them, the trans will finish the poker run or race, but be stuck in gear, but get you home.
What the shops do is surface grind the steels to allow for more plates to increase the co-efficiency of friction ( surface area) and try to drill oil passages out to make clutch pack work faster and reduce slippage in engagement.
This is also done by modifying pumps.
Yes , I've been inside of a few transmissions too. BBB

Just spin the pump around. It has arrows on it.... BBB

If needed i am in orlando and know how to work on these. If you want to order the parts i would be happy to work on them for you. email me at [email protected]

if you decide on getting different trannys, let me know when you are going to sell the 71c. [email protected]