bell houseing

raymond workman · Post by **raymond workman** » Sun Mar 09, 2008 9:27 pm

Does anybody know if a borg warner trans model 71c has the same bolt pattern as a 72c I am going to repower my boat from 351 fords to 440 chrysler and hopeing the pattern is the same.

prowlersfish · Post by **prowlersfish** » Mon Mar 10, 2008 6:47 am

Yes the are the same , the flange at the output shaft could diffrent but but you could swap them if they are.

raymond workman · Post by **raymond workman** » Mon Mar 10, 2008 10:24 am

Thanks that is another plus for the swap.

raymond workman · Post by **raymond workman** » Thu Mar 13, 2008 6:59 pm

Hey pual do you think these tranny will hold up to the motor or can they be upgraded to hold up or do I need to be looking for some 72 models I was told buy someone on another forum not to even try they would not hold up. I wasnt trying to build a speed boat but couldnt pass on the motors a rebuild was going to run 4000k on just 2 long blocks alone and I still was going to need everything because mine have not ran in 5yrs and are locked up tite and the swap would be fairly easy because I have to replace the back deck and tanks and on and on I have more time than money and the desire for boats and water will allways be their.So i could take more time and put it back together with a little more power at a fraction of the cost. and get the best bang for my buck. What size do you think my drive shafts are and will they hold up or will I need to replace them as well. thx ray

prowlersfish · Post by **prowlersfish** » Thu Mar 13, 2008 8:05 pm

Raymond , the 71 will work but it will be at near its limit , to make it last the key would be to prop it lite I belive that eng is rated at 4000 rpm if you prop it to turn 4400 you will reduce the load on the gear box . If you use the props you have know you should have no issues as long as you do not abuse it.

As far as the shafts.I will guess you you have a 1 to 1 gear so I asume you have a 1" shaft, again you are near the limits but still within them
with a low safety factor , again prop it light and you should be ok . I am also asuming you have a aqumet19 or better shaft .

sure you would be better off with 72 gears and larger shafts , but if its what I have then I would use it. we did a boat like with with 454s got by with it ,the gears and the shafts held up . thats more then i can say for the engines .

if you up grade to 72 gears later its a drop in so no big deal .

raymond workman · Post by **raymond workman** » Thu Mar 13, 2008 9:56 pm

I have 12 in props dont know the pitch what would you run to acheive that goal of 4400 thx ray

prowlersfish · Post by **prowlersfish** » Thu Mar 13, 2008 10:41 pm

Raymond , do you know what rpm you were turning before and what was the hp of the old engines ?

raymond workman · Post by **raymond workman** » Thu Mar 13, 2008 11:32 pm

have never had boat in water old motors were 233hr mercrusers thx ray

prowlersfish · Post by **prowlersfish** » Sat Mar 15, 2008 6:53 pm

Raymond , sorry it took so long to get back with you , had to do some thinking on this I am thinking you running a 12x12 prop , I would repitch it to 12x12 and see how it goes be for buying new props . If your props not 12x12 I would still try adding 2" pitch . uless larger then that then I would try what you have . every boat is diffrent so what works on one F30 may not be just right on another one . once you have it in the water and runing you have the base to start fine tunning the props .