Trojan Boat Forum

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.

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

Thanks that is another plus for the swap.

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

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 .

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

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

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

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 .