Setback allows you to run a shorter motor shaft length due to the water rolling "up" off the bottom. by running a shorter length(or jacking the motors), you have less resistance from the lower units running through the water. 30" is a deep bracket eith a lot of setback, and as Ryan said, 25" motors will be kinda deep. It should run better overall with no bracket, and approx 10" - 12" setback/jackplates. I love the bracket/swimplatform on my v-hull, but not sure how well it would work on a cat.

Ryan,

The bracket is a full platform like on my pantera, not a gil tube type.

ok i gotcha. i like the jack plates first because the are smaller and lighter, and they are adjustable. also they wont add near as much overall length to my boat.

but the bracket gives me the swim platform. and the option to add a third motor.........what to do what to do. the cost of each it about the same.

would it be better to run 10-12 inch jackplatees with the 25" shaft or the 30 inch bracket with say a 20" shaft?

and how big of a difference are we talkin here? just a mph or two or a big difference in mph, ride, handling etc.....?

i am willing to go either way.

I'd be curious to know this answer as well. I just don't remember any Shadows with setback brackets on them.

Personally I would go with the jackplates(manual is fine, and will save you $$, I prefer CMC plates) on the cat, even if ya went with 20" motors. The advantage of the jack is that it is adjustable for fine tuning. I hear ya on the swim platform, but things can be fabricated to make ya something that will at least get you a ladder mount to get in and out. As far as how much of a difference it will make depends on a few things.............

1 - Setup, if ya get the height wrong with the bracket you are pretty much stuck(my bracket has like 16 half inch bolts holding it thru the transom), other than manually adjusting the motor height using one of 5 holes on the clamp bracket(get out the engine hoist).

2 - Center of Gravity(OK, so that is also part of setup), 30" setback is a LOTTT, especially if you decide on triples(which personally I wouldnt, those 250's can be modified to OVER 300HP reliably by either Simon Marine, or Shaun Torrente).

3 - 25" motors, are gonna be a little tall for that boat, without jackplates, either the bracket will be mounted way high on the transom, or your props will be buried, and you will be forced to run a lower pitch to get ya to the 5400- 5800rpm the 250's make the most power at.

I would say if it is poorly setup, you could be talking up to a 10MPH difference, some of which could be fixed by moving the motors up on the clamps, but then you still have powerheads 30" back on the bracket, and way up high throwing off C.G.??? It is kinda a crapsoot. Since you said you were doing tanks anyway, you could put the tanks further forward along with batteries etc to move your C.G. back forward some, but it is a balancing act. Her eis a video of my Pantera, I realize it is a vee hull, single, and I don't have a lot of experience with cat's, but look at the attitude of this thing running, it is almost too flat, I need my C.G. to move a bit back(and a few more HP:drink:)

http://www.youtube.com/watch?v=b-_4V9zkVgQ

We had a 28 Eliminator at my job , it had a big swimplatform motor bracket set up , it had at least 30 inches setback, running 2 300X`s , i think 20 inch standard midsections , i thought it was weird because the yellow b bracket was a different shade of yellow than the hull, but it was factory , anyway took a while to plane off but the boat was fast , I know its a totally different style hull, but i thought i would mention it .

any thoughts on fuel tank placement on the boat? it had bladders under the floor when set up with the I/O setup. with the outboards being lighter would this change the necessary placement of the tanks/bladdders? and can i switch to tanks or do i have to stay with the bladder setup? heeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeellp! lmao

I don't see why you couldn't run tanks.mill measure the placement of mine but it had twin 76 gal tanks that started approx 2 ft from back of the boat.

Some nice CMC jackplates is what id do

Definitely go with the jack plates. You should be able to place tanks in the forward portion of the engine room. You may have to build a floor for them since the stringers were set up for I/O. These are a great hull design, my Chris Cat is the same hull only slightly wider for Big Blocks. Shadows had small blocks.

T2x is the fellow who helped design and build these boats.

Wannabe