what kind of HP increase would i see with tth on this thing its run through the bravo one out drive right now

its not a jet 

its not a jet 

Thanks bud I was being sarcastic.   back to the hallet, nice boat bud.  Im sure headers would help but enough to cut holes in that beautiful boat? btw lets see more pics of her.

what kind of HP increase would i see with tth on this thing its run through the bravo one out drive right now

What motor and what exhaust?

On our 330 HP 454, we saw just under 15 HP on the propshaft dyno going from the thru hub to IMCO thru transoms, I would think headers should be good for a tad more...The biggest problem with thru transom headers if they are not water jacketed is the heat build up on a closed engine compartment, it can be somewhat parasitic to the air charge (too warm)...

GT

It is a stoke merc package 454 330 and has stoke risers

what kind of HP increase would i see with tth on this thing its run through the bravo one out drive right now

Harry Nearly any significant increase in "breathing" will help that MC application . The thru hub deal is restrictive , Assuming you currently have a rear dump "y" pipe set up , you'll need some manifolds like the Drakes Skip mentioned , rizers, tail pipes,tips s bend and a block off for the "Y" current deal . You will also want to Improve the Upper end as well to compliment the exaust changes (improved intake and Carb) I suspect that motor has peanut port heads originally (somewhat restrictive as an NA as well) Tom  

BTW most modern aftermarket Center rize set ups , eg Eddie, Rex ,Dana etc will support 700+ hp I chose Eddie myself

Heres some Danas we use recently

WOW thats PERDY there Tom

Toms always got the nice Sh#t!