25 AT drive question
 

I posted this in the AT section:

Here is what I have done to myself. New motor is off dyno. Made great power and torque. Peak torque of 1072 ft# is at 4700RPM and 1008 HP at 5300RPM with small Procharger. I plan on detuning this thing down but am still going to be in the 800-900 torque and 750-800 HP range. Problem is I still have a Bravo 1 drive with 29 4 blade prop. I know that I will need to do some upgrades. I do most of my time on Lake Michigan. Prop centerline is about 5" from bottom. What is the best way to go? -2" Imco? B-Max? 1.36 gear? 4 blade 36? Upgrade trim tabs? I will spend the money but really don't want to. lol. Again boat is a 1998 25 AT with me wife and two kids. I guess give me an education. FYI I am a drag racer and just learning the boat life style. Thanks,Kyle

All American drive service. I believe he has a package for that hp range. 280 k-planes are sufficient for that boat.

Noone has a bravo package for 900tq, 800+ hp .. let`s get real.You can put all kinds of woodoo on the drive but at the end of the day you still have the small bravo gears.
I ate 1 drive a year with a 600SC on Lake Michigan (In a 25' AT) Cryoed. special tower, ribbed top cap blah blah blah .. didn`t help.
A 25' boat will be mostly in the air on Lake Michigan it`s the reentry that puts most of the upper gear killing stress on the drive.
I hated it, my kidneys hated it, my back hated me.
Anything with Bravo gears is going to be in serious pain.

IMCO SCX is my suggestion. My other suggestion is to get a longer boat :-)
Going to a 33' OL was night and day.

Leaning towards a SCX upper with -2 SC lower. What gears? What prop? Anyone run a short drive on a 25 AT? I am getting different answers from everyone I talk to? Thoughts on tabs?

I would go with a 1.36 SCX upper and lower. The boat is going to be soooooo fast that the SCX lower slowing it down a few mph won't matter.

Good point lol. It will be fast , mine with 600SC would do about 80mph and it scary chined walked at that speed. I didn`t know how to make it stop. I guess you`ll find out if you can "drive thru it"

For the 600SC (600hp) I had Mercury recommends :

900 ftlbs and 800 hp in a 25 AT.................Have fun. Mine was a tired stock 502 mag mpi... about 68 mph and it got a bit hairy even at that speed on Lake Erie. I guessing high 80's to low 90's and it will accelerate like a rocket.

The SC lower will still have the stock Merc gears in it. Go SCX upper and lower. Or Arneson (someone had to say it! lol!).

Oh and yess I do want to go for a ride..... Thanks for asking...:asskiss: